- Lipase-catalyzed kinetic resolution of Z-configured homoallylic alcohols
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Racemic Z homoallylic alcohols were prepared by the BuSnCl3-catalyzed addition of aldehydes to 1-(tributylstannyl)-2-butene. These alcohols were resolved for the first time by lipase-catalyzed enantioselective acetylation in up to 98% enantiomeric purity.
- Adam, Waldemar,Saha-Moeller, Chantu R.,Schmid, Katharina S.
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- Chain Walking as a Strategy for Iridium-Catalyzed Migratory Amidation of Alkenyl Alcohols to Access α-Amino Ketones
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Catalytic carbon-nitrogen bond formation in hydrocarbons is an appealing synthetic tool to access valuable nitrogen-containing compounds. Although a number of synthetic approaches have been developed to construct a bifunctional α-amino carbonyl scaffold in this realm, installation of an amino functionality at the remote and unfunctionalized aliphatic sites remains underdeveloped. Here we present a tandem iridium catalysis that enables the redox-relay amidation of alkenyl alcohols via chain walking and metal-nitrenoid transfer, which eventually offers a new route to various α-amino ketones with excellent regioselectivity. The virtue of this transformation is that an unrefined isomeric mixture of alkenyl alcohols can be utilized as the readily available starting materials to lead to the regioconvergent amidation. Mechanistic investigations revealed that the reaction proceeds via a tandem process involving two key components of redox-relay chain walking and intermolecular nitrenoid transfer with the assistance of hydrogen bonding, thus representing the competence of Ir catalysis for the olefin migratory C-N coupling with high efficiency and exquisite selectivity.
- Baek, Seung Beom,Chang, Sukbok,Hwang, Yeongyu,Kim, Dongwook
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supporting information
p. 4277 - 4285
(2022/03/08)
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- Homoleptic cobalt(II) phenoxyimine complexes for hydrosilylation of aldehydes and ketones without base activation of cobalt(II)
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Air-stable, easy to prepare, homoleptic cobalt(II) complexes bearing pendant-modified phenoxyimine ligands were synthesized and determined. The complexes exhibited high catalytic performance for reducing aldehydes and ketones via catalytic hydrosilylation, where a hydrosilane and a catalytic amount of the cobalt(II) complex were added under base-free conditions. The reaction proceeded even in the presence of excess water, and excellent functional-group tolerance was observed. Subsequent hydrolysis gave the alcohol in high yields. Moreover, H2O had a critical role in activation of the Co(II) catalyst with hydrosilane. Several additional results also indicated that the cobalt(II) center acts as an active catalyst in the hydrosilylation of aldehydes and ketones.
- Hori, Momoko,Ishikawa, Ryuta,Koga, Yuji,Matsubara, Kouki,Mitsuyama, Tomoaki,Shin, Sayaka
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supporting information
p. 1379 - 1387
(2021/05/29)
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- Highly Active Cooperative Lewis Acid—Ammonium Salt Catalyst for the Enantioselective Hydroboration of Ketones
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Enantiopure secondary alcohols are fundamental high-value synthetic building blocks. One of the most attractive ways to get access to this compound class is the catalytic hydroboration. We describe a new concept for this reaction type that allowed for exceptional catalytic turnover numbers (up to 15 400), which were increased by around 1.5–3 orders of magnitude compared to the most active catalysts previously reported. In our concept an aprotic ammonium halide moiety cooperates with an oxophilic Lewis acid within the same catalyst molecule. Control experiments reveal that both catalytic centers are essential for the observed activity. Kinetic, spectroscopic and computational studies show that the hydride transfer is rate limiting and proceeds via a concerted mechanism, in which hydride at Boron is continuously displaced by iodide, reminiscent to an SN2 reaction. The catalyst, which is accessible in high yields in few steps, was found to be stable during catalysis, readily recyclable and could be reused 10 times still efficiently working.
- Titze, Marvin,Heitk?mper, Juliane,Junge, Thorsten,K?stner, Johannes,Peters, René
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supporting information
p. 5544 - 5553
(2021/02/05)
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- Base-induced Sommelet–Hauser rearrangement of N-(α-(2-oxyethyl)branched)benzylic glycine ester-derived ammonium salts via a chelated intermediate
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The base-induced Sommelet–Hauser (S–H) rearrangement of N-(α-branched)benzylic glycine ester-derived ammonium salts 1 was investigated. When the α-branched substituent was a simple alkyl, such as a methyl or butyl, desired S–H rearrangement product 2 was obtained in low yield with formation of the [1,2] Stevens rearranged 4 and Hofmann eliminated products 5 and 6. However, when the α-branched substituent had a 2-oxy moiety, such as 2-acetoxyethyl or 2-benzoyloxyethyl, the yields of 2 were improved. These results could be explained by formation of chelated intermediate C that stabilizes the carbanionic ylide, and the subsequent initial dearomative [2,3] sigmatropic rearrangement would be accelerated. The existence of C was supported by mechanistic experiments. This enhancement effect is not very strong or effective; however, it will expand the synthetic usefulness of ammonium ylide rearrangements.
- Baba, Souya,Hirano, Kazuki,Tayama, Eiji
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supporting information
(2020/03/13)
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- SOLVENTS FOR ORGANOMETALLIC REAGENTS
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In an embodiment, the present disclosure pertains to a solvent including a hydrocarbon oligomer with at least 20 carbon atoms, where the hydrocarbon oligomer has at least one of a low viscosity, a low vapor pressure, and a high flashpoint. In another embodiment, the present disclosure pertains to a solution including a poly(α-olefin) and a reactive organometallic reagent. In a further embodiment, the present disclosure pertains to a solution including an oligomeric hydrocarbon and a reactive organometallic reagent. In an additional embodiment, the present disclosure pertains to a method for creating a solution, where the method includes adding a reactive organometallic reagent to an oligomeric hydrocarbon.
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Paragraph 0017; 0033; 0034; 0049
(2020/02/23)
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- Efficient Transfer Hydrogenation of Ketones using Methanol as Liquid Organic Hydrogen Carrier
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Herein, we demonstrate an efficient protocol for transfer hydrogenation of ketones using methanol as practical and useful liquid organic hydrogen carrier (LOHC) under Ir(III) catalysis. Various ketones, including electron-rich/electron-poor aromatic ketones, heteroaromatic and aliphatic ketones, have been efficiently reduced into their corresponding alcohols. Chemoselective reduction of ketones was established in the presence of various other reducible functional groups under mild conditions.
- Garg, Nidhi,Paira, Soumen,Sundararaju, Basker
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p. 3472 - 3476
(2020/05/29)
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- Enzymatic Primary Amination of Benzylic and Allylic C(sp3)-H Bonds
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Aliphatic primary amines are prevalent in natural products, pharmaceuticals, and functional materials. While a plethora of processes are reported for their synthesis, methods that directly install a free amine group into C(sp3)-H bonds remain unprecedented. Here, we report a set of new-to-nature enzymes that catalyze the direct primary amination of C(sp3)-H bonds with excellent chemo-, regio-, and enantioselectivity, using a readily available hydroxylamine derivative as the nitrogen source. Directed evolution of genetically encoded cytochrome P411 enzymes (P450s whose Cys axial ligand to the heme iron has been replaced with Ser) generated variants that selectively functionalize benzylic and allylic C-H bonds, affording a broad scope of enantioenriched primary amines. This biocatalytic process is efficient and selective (up to 3930 TTN and 96percent ee), and can be performed on preparative scale.
- Jia, Zhi-Jun,Gao, Shilong,Arnold, Frances H.
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supporting information
p. 10279 - 10283
(2020/07/27)
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- Direct transformation of aryl 2-pyridyl esters to secondary benzylic alcohols by nickel relay catalysis
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A direct transformation of aryl esters to secondary benzylic alcohols via tandem Ni-catalyzed cross-coupling reactions of aromatic 2-pyridyl esters with alkyl zinc reagents and carbonyl group reduction by Ni-H species is achieved. Preliminary mechanistic studies reveal that the Ni-H species is generated in situ via β-hydride elimination of the Negishi reagents. The reaction is catalyzed by bench-stable nickel salts under mild conditions with wide functional group tolerance.
- Wu, Xianqing,Li, Xiaobin,Huang, Wenyi,Wang, Yun,Xu, Hui,Cai, Liangzhen,Qu, Jingping,Chen, Yifeng
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p. 2453 - 2458
(2019/03/29)
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- Reductive C-O, C-N, and C-S Cleavage by a Zirconium Catalyzed Hydrometalation/β-Elimination Approach
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A zirconium catalyzed reductive cleavage of Csp3 and Csp2 carbon-heteroatom bonds is reported that makes use of a tethered alkene functionality as a traceless directing group. The reaction is successfully demonstrated on C-O, C-N, and C-S bonds and proposed to proceed via a hydrozirconation/β-heteroatom elimination sequence of an in situ formed zirconium hydride catalyst. The positional isomerization of the catalyst further enables the cleavage of homoallylic ethers and the removal of terminal allyl and propargyl groups.
- Matt, Christof,K?lblin, Frederic,Streuff, Jan
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supporting information
p. 6983 - 6988
(2019/09/09)
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- NBS-mediated synthesis of β-keto sulfones from benzyl alcohols and sodium arenesulfinates
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An efficient synthetic route towards the synthesis of β-keto sulfones has been developed from secondary benzyl alcohols using N-bromosuccinimide (NBS). The present protocol utilizes NBS as oxidant as well as brominating agent, readily accessible benzyl alcohols and sodium arenesulfinates as the sulfonylating reagent under mild conditions. The control experiments revealed that the reaction proceeds via oxidation of alcohol to ketone, α-bromination of ketone and nucleophilic substitution by sodium arenesulfinate. Furthermore, the efficiency of the methodology was tested with a gram scale reaction and also shown the synthetic utility.
- Muneeswara, Madithedu,Sundaravelu, Nallappan,Sekar, Govindasamy
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supporting information
p. 3479 - 3484
(2019/05/21)
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- Regioselective Vinylation of Remote Unactivated C(sp3)?H Bonds: Access to Complex Fluoroalkylated Alkenes
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Regioselective incorporation of a particular functional group into aliphatic sites by direct activation of unreactive C?H bonds is of great synthetic value. Despite advances in radical-mediated functionalization of C(sp3)?H bonds by a hydrogen-atom transfer process, the site-selective vinylation of remote C(sp3)?H bonds still remains underexplored. Reported herein is a new protocol for the regioselective vinylation of unactivated C(sp3)?H bonds. The remote C(sp3)?H activation is promoted by a C-centered radical instead of the commonly used N and O radicals. The reaction possesses high product diversity and synthetic efficiency, furnishing a plethora of synthetically valuable E alkenes bearing tri-/di-/mono-fluoromethyl and perfluoroalkyl groups.
- Wu, Shuo,Wu, Xinxin,Wang, Dongping,Zhu, Chen
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supporting information
p. 1499 - 1503
(2019/01/04)
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- Regioselective Sulfonylvinylation of the Unactivated C(sp3)-H Bond via a C-Centered Radical-Mediated Hydrogen Atom Transfer (HAT) Process
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Given the similarity of multiple sp3 C-H bonds in electronic properties and bond dissociation energy (BDE), regioselective sp3 C-H bond functionalization remains a paramount challenge. Here, we report a C-centered radical-mediated approach for site-specific sulfonylvinylation of the C(sp3)-H bond via the hydrogen atom transfer (HAT) process. The reaction features mild conditions, broad substrate scope, and high regioselectivity and stereoselectivity, manifesting the nontrivial synthetic potential.
- Yang, Shan,Wu, Xinxin,Wu, Shuo,Zhu, Chen
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supporting information
p. 4837 - 4841
(2019/06/24)
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- A Practical and Stereoselective In Situ NHC-Cobalt Catalytic System for Hydrogenation of Ketones and Aldehydes
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Homogeneous catalytic hydrogenation of carbonyl groups is a synthetically useful and widely applied organic transformation. Sustainable chemistry goals require replacing conventional noble transition metal catalysts for hydrogenation by earth-abundant base metals. Herein, we report how a practical in situ catalytic system generated by easily available pincer NHC precursors, CoCl2, and a base enabled efficient and high-yielding hydrogenation of a broad range of ketones and aldehydes (over 50 examples and a maximum turnover number [TON] of 2,610). This is the first example of NHC-Co-catalyzed hydrogenation of C=O bonds using flexible pincer NHC ligands consisting of a N-H substructure. Diastereodivergent hydrogenation of substituted cyclohexanone derivatives was also realized by fine-tuning of the steric bulk of pincer NHC ligands. Additionally, a bis(NHCs)-Co complex was successfully isolated and fully characterized, and it exhibits excellent catalytic activity that equals that of the in-situ-formed catalytic system. Catalytic hydrogenation is a powerful tool for the reduction of organic compounds in both fine and bulk chemical industries. To improve sustainability, more ecofriendly, inexpensive, and earth-abundant base metals should be employed to replace the precious metals that currently dominate the development of hydrogenation catalysts. However, the majority of the base-metal catalysts that have been reported involve expensive, complex, and often air- and moisture-sensitive phosphine ligands, impeding their widespread application. From a mixture of the stable CoCl2, imidazole salts, and a base, our newly developed catalytic system that formed easily in situ enables efficient and stereoselective hydrogenation of C=O bonds. We anticipate that this easily accessible catalytic system will create opportunities for the design of practical base-metal hydrogenation catalysts. A practical in situ catalytic system generated by a mixture of easily available pincer NHC precursors, CoCl2, and a base enabled highly efficient hydrogenation of a broad range of ketones and aldehydes (over 50 examples and up to a turnover number [TON] of 2,610). Diastereodivergent hydrogenation of substituted cyclohexanone derivatives was also realized in high selectivities. Moreover, the preparation of a well-defined bis(NHCs)-Co complex via this pincer NHC ligand consisting of a N-H substructure was successful, and it exhibits equally excellent catalytic activity for the hydrogenation of C=O bonds.
- Zhong, Rui,Wei, Zeyuan,Zhang, Wei,Liu, Shun,Liu, Qiang
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supporting information
p. 1552 - 1566
(2019/06/14)
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- Highly Focused Library-Based Engineering of Candida antarctica Lipase B with (S)-Selectivity Towards sec-Alcohols
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Candida antarctica lipase B (CALB) is one of the most extensively used biocatalysts in both academia and industry and exhibits remarkable (R)-enantioselectivity for various chiral sec-alcohols. Considering the significance of tailor-made stereoselectivity in organic synthesis, a discovery of enantiocomplementary lipase mutants with high (R)- and (S)-selectivity is valuable and highly desired. Herein, we report a highly efficient directed evolution strategy, using only 4 representative amino acids, namely, alanine (A), leucine (L), lysine (K), tryptophan (W) at each mutated site to create an extremely small library of CALB variants requiring notably less screening. The obtained best mutant with three mutations W104V/A281L/A282K displayed highly reversed (S)-selectivity towards a series of sec-alcohol with E values up to 115 (conv. 50%, ee 94%). Compared with the previously reported (S)-selective CALB variant, W104A, a single mutation provided less selectivity, while the synergistic effects of three mutations in the best variant endow better (S)-selectivity and a broader substrate scope than the W104A variant. Structural analysis and molecular dynamics simulation unveiled the source of reversed enantioselectivity. (Figure presented.).
- Cen, Yixin,Li, Danyang,Xu, Jian,Wu, Qiongsi,Wu, Qi,Lin, Xianfu
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supporting information
p. 126 - 134
(2018/12/05)
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- Synthesis, characterization of novel Nickel(II) complexes with PxNy-Type ligands and their application in reduction of ketones
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Novel nickel(II) complexes 1 and 2 could be conveniently prepared using PxNy-type ligands and easily available NiCl2·6H2O as a starting material. Furthermore, we obtained the single crystals suitable for X-ray diffraction to confirm the structure of these two nickel(II) complexes. With the well-designed nickel(II) complex, the hydrogenation of a wide range of ketones proceeded smoothly under relative mild reaction conditions, affording the corresponding alcohols with high isolated yields.
- Wang, Zhe,Yu, Shen-Luan,Wei, Zan-Bin,An, Dong-Li,Li, Yan-Yun,Gao, Jing-Xing
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supporting information
(2019/08/12)
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- Deoxygenative cross-electrophile coupling of benzyl chloroformates with aryl iodides
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This work describes Ni-catalyzed cross-electrophile coupling of benzyl chloroformate derivatives with aryl iodides that generates a wide range of diaryl methane products. The mild reaction conditions merit the C-O bond radical fragmentation of benzyl chloroformates via halide abstraction or a single electron reduction by a Ni catalyst. This work offers a new substrate type for cross-electrophile couplings.
- Pan, Yingying,Gong, Yuxin,Song, Yanhong,Tong, Weiqi,Gong, Hegui
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supporting information
p. 4230 - 4233
(2019/05/06)
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- Electron transfer-induced reduction of organic halides with amines
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Reduction of a variety of organo halides was examined by using amines as a sacrificial hydrogen source. UV light-induced reduction of vinyl and aryl halides with triethylamine proceeded smoothly to give the corresponding reduced products. High temperature heating also caused the reduction and DABCO (1,4-diazabicyclo[2.2.2]octane) also served as a good reducing reagent.
- Fukuyama, Takahide,Fujita, Yuki,Miyoshi, Hayato,Ryu, Ilhyong,Kao, Shih-Chieh,Wu, Yen-Ku
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supporting information
p. 5582 - 5585
(2018/06/04)
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- A PROCESS FOR PREPARING FUNCTIONAL POLYMERS THROUGH ADDITION OF AMINO AND POLYMERYL GROUPS TO ALDEHYDE MOIETIES
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The present disclosure relates to a one-pot process for synthesizing functional compounds or functional polymers by reacting an aldehyde with an alkyl-zinc or polymeryl-zinc composition in the presence of a specific Lewis acid, wherein the reaction is rapid and facile at high temperatures.
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Paragraph 0006
(2018/10/19)
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- N-Heterocyclic Carbene Iron(III) Porphyrin-Catalyzed Intramolecular C(sp3)–H Amination of Alkyl Azides
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Metal-catalyzed intramolecular C?H amination of alkyl azides constitutes an appealing approach to alicyclic amines; challenges remain in broadening substrate scope, enhancing regioselectivity, and applying the method to natural product synthesis. Herein we report an iron(III) porphyrin bearing axial N-heterocyclic carbene ligands which catalyzes the intramolecular C(sp3)–H amination of a wide variety of alkyl azides under microwave-assisted and thermal conditions, resulting in selective amination of tertiary, benzylic, allylic, secondary, and primary C?H bonds with up to 95 % yield. 14 out of 17 substrates were cyclized selectively at C4 to give pyrrolidines. The regioselectivity at C4 or C5 could be tuned by modifying the reactivity of the C5–H bond. Mechanistic studies revealed a concerted or a fast re-bound mechanism for the amination reaction. The reaction has been applied to the syntheses of tropane, nicotine, cis-octahydroindole, and leelamine derivatives.
- Shing, Ka-Pan,Liu, Yungen,Cao, Bei,Chang, Xiao-Yong,You, Tingjie,Che, Chi-Ming
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supporting information
p. 11947 - 11951
(2018/09/11)
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- Safer solvents for reactive organometallic reagents
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This paper describes the use of poly(α -olefin)s (PAOs) as safer alternatives to cyclohexane, hexanes, and heptane as solvents for alkyllithium reagents. While PAOs like any alkane are flammable, PAOs do not readily catch on fire because they contain 20 or more carbon atoms, a low volatility, and have a high flash point vis-à-vis alkanes like hexane. Also unlike conventional alkanes, PAOs can be quantitatively separated from polar organic solvents and polar organic products either by a simple gravity separation or by an extraction after a reaction. Any leaching of the PAO solvent into a polar phase during such a separation can be minimized by addition of small amounts of water to the polar phase. However, while these PAO solvents have some physical differences from conventional low molecular weight volatile alkanes, they otherwise behave like alkanes and alkyllithium reagents in these PAO solvents can used in their conventional reactions in these PAO solvents.
- Malinski, Thomas J.,Bergbreiter, David E.
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supporting information
p. 3926 - 3929
(2018/10/02)
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- Improved Enantioselectivity of Subtilisin Carlsberg towards Secondary Alcohols by Protein Engineering
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Generally, the catalytic activity of subtilisin Carlsberg (SC) for transacylation reactions with secondary alcohols in organic solvent is low. Enzyme immobilization and protein engineering was performed to improve the enantioselectivity of SC towards secondary alcohols. Possible amino-acid residues for mutagenesis were found by combining available literature data with molecular modeling. SC variants were created by site-directed mutagenesis and were evaluated for a model transacylation reaction containing 1-phenylethanol in THF. Variants showing high E values (>100) were found. However, the conversions were still low. A second mutation was made, and both the E values and conversions were increased. Relative to that shown by the wild type, the most successful variant, G165L/M221F, showed increased conversion (up to 36 %), enantioselectivity (E values up to 400), substrate scope, and stability in THF.
- Dorau, Robin,G?rbe, Tamás,Svedendahl Humble, Maria
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p. 338 - 346
(2017/12/26)
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- Grignard Reagents on a Tab: Direct Magnesium Insertion under Flow Conditions
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An on-demand preparation of organomagnesium reagents is presented using a new flow protocol. The risks associated with the activation of magnesium are circumvented by a new on-column initiation procedure. Required amounts of solutions with a precise titration were obtained. Telescoped flow or batch reactions allow access to a diverse set of functional groups.
- Huck, Lena,De La Hoz, Antonio,Díaz-Ortiz, Angel,Alcázar, Jesus
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supporting information
p. 3747 - 3750
(2017/07/26)
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- Forging C-C Bonds with Hindered Nucleophiles and Carbonyl Electrophiles: Reactivity and Selectivity of Allylic Tin Reagents/n-BuLi
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Under activation with n-BuLi, trialkylstannanes containing crotyl-, geranyl-, and phenyldienylmethyl appendages were reacted with efficiency and selectivity to various ketone and enone electrophiles with low reactivity. The straightforward process gives access to tertiary alcohols that are vicinal to quaternary carbons. With α,α′-dimethoxy-γ-pyrone, on the other hand, the grafting of a dienyl side chain was effected to prepare dienyl α′-methoxy-γ-pyrone in a stereo- and regioselective and convergent manner. Furthermore, the advantages of this route were highlighted for the preparation of organolithium species at low temperature with the formation of a minimum amount of salts. Synthetic manipulations were demonstrated to illustrate the potential of the chemistry for constructing acyclic and cyclic terpene scaffolds.
- Cormier, Morgan,Ahmad, Maha,Maddaluno, Jacques,De Paolis, Micha?l
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p. 4920 - 4927
(2018/02/07)
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- Dual cobalt-copper light-driven catalytic reduction of aldehydes and aromatic ketones in aqueous media
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We present an efficient, general, fast, and robust light-driven methodology based on earth-abundant elements to reduce aryl ketones, and both aryl and aliphatic aldehydes (up to 1400 TON). The catalytic system consists of a robust and well-defined aminopyridyl cobalt complex active for photocatalytic water reduction and the [Cu(bathocuproine)(Xantphos)](PF6) photoredox catalyst. The dual cobalt-copper system uses visible light as the driving-force and H2O and an electron donor (Et3N or iPr2EtN) as the hydride source. The catalytic system operates in aqueous mixtures (80-60% water) with high selectivity towards the reduction of organic substrates (>2000) vs. water reduction, and tolerates O2. High selectivity towards the hydrogenation of aryl ketones is observed in the presence of terminal olefins, aliphatic ketones, and alkynes. Remarkably, the catalytic system also shows unique selectivity for the reduction of acetophenone in the presence of aliphatic aldehydes. The catalytic system provides a simple and convenient method to obtain α,β-deuterated alcohols. Both the observed reactivity and the DFT modelling support a common cobalt hydride intermediate. The DFT modelled energy profile for the [Co-H] nucleophilic attack to acetophenone and water rationalises the competence of [CoII-H] to reduce acetophenone in the presence of water. Mechanistic studies suggest alternative mechanisms depending on the redox potential of the substrate. These results show the potential of the water reduction catalyst [Co(OTf)(Py2Tstacn)](OTf) (1), (Py2Tstacn = 1,4-di(picolyl)-7-(p-toluenesulfonyl)-1,4,7-triazacyclononane, OTf = trifluoromethanesulfonate anion) to develop light-driven selective organic transformations and fine solar chemicals.
- Call, Arnau,Casadevall, Carla,Acu?a-Parés, Ferran,Casitas, Alicia,Lloret-Fillol, Julio
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p. 4739 - 4749
(2017/07/10)
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- Ruthenium(III)-Catalyzed β-Alkylation of Secondary Alcohols with Primary Alcohols
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A Ru(III)-NNN complex bearing a pyridyl-supported pyrazolyl-imidazolyl ligand was synthesized and utilized as the catalyst for the direct β-alkylation of secondary alcohols with primary alcohols. β-Alkylated secondary alcohols were obtained in moderate to high yields with water formed as the byproduct through a hydrogen borrowing pathway. The present protocol provides a concise atom-economical and environmentally benign method for C-C bond formation.
- Wang, Qingfu,Wu, Kaikai,Yu, Zhengkun
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p. 1251 - 1256
(2016/06/01)
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- Improved enantioselectivity of thermostable esterase ST0071 from archaeon Sulfolobus tokodaii by site-saturation mutagenesis
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An archaeon GGG(A)X-type esterase (ST0071) can catalyze the hydrolysis of various acetates of secondary alcohols, but shows low enantioselectivity. Using structure-guided site-saturation mutagenesis, we successfully identified a G274W variant that has excellent selectivity compared with that of wild-type ST0071.
- Ozaki, Masanaru,Kawakami, Norifumi,Ohta, Hiromichi,Miyamoto, Kenji
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p. 249 - 252
(2016/12/16)
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- Catalytic asymmetric addition of aldehydes using organolithium reagents in the presence of commercial available chiral diol ligands
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An efficient method for the catalytic asymmetric additions to aldehydes using organolithium reagents and titanium(IV) isopropoxide in the presence of commercially available and relatively inexpensive diol ligands, such as (S)-BINOL or D-TADDOL has been developed. Good to excellent yields (up to 92%) and enantioselectivities (up to 94%) of the corresponding secondary alcohol products can be obtained following a simple procedure at relatively mild reaction temperatures.
- Zong, Hua,Huang, Huayin,Song, Ling
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supporting information
p. 1069 - 1074
(2016/10/11)
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- Highly Active and Selective Manganese C=O Bond Hydrogenation Catalysts: The Importance of the Multidentate Ligand, the Ancillary Ligands, and the Oxidation State
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The replacement of expensive noble metals by earth-abundant transition metals is a central topic in catalysis. Herein, we introduce a highly active and selective homogeneous manganese-based C=O bond hydrogenation catalyst. Our catalyst has a broad substrate scope, it is able to hydrogenate aryl–alkyl, diaryl, dialkyl, and cycloalkyl ketones as well as aldehydes. A very good functional group tolerance including the quantitative and selective hydrogenation of a ketone in the presence of a non-shielded olefin is observed. In Mn hydrogenation catalysis, the combination of the multidentate ligand, the oxidation state of the metal, and the choice of the right ancillary ligand is crucial for high activity. This observation emphasizes an advantage and the importance of homogeneous catalysts in 3d-metal catalysis. For coordination compounds, fine-tuning of a complex coordination environment is easily accomplished in comparison to enzyme and/or heterogeneous catalysts.
- Kallmeier, Fabian,Irrgang, Torsten,Dietel, Thomas,Kempe, Rhett
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supporting information
p. 11806 - 11809
(2016/11/16)
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- Expanding substrate scope of lipase-catalyzed transesterification by the utilization of liquid carbon dioxide
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Secondary alcohols having bulky substituents on both sides of the chiral center are often poor substrates for most lipases. Here we reported that substrate scopes of two of the most used lipases, Candida antarctica lipase B and Burkholderia cepacia lipase, were found to be expanded toward more bulky secondary alcohols such as 1-phenyl-1-dodecanol and 2-methyl-1-phenyl-1-propanol by simply using them in liquid carbon dioxide as a solvent. The effects of solvents, reaction pressure, and pre-treatment of the enzyme with liquid CO2on this acceleration phenomenon were also studied.
- Hoang, Hai Nam,Matsuda, Tomoko
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p. 7229 - 7234
(2016/10/26)
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- The directing group wins over acidity: kinetically controlled regioselective lithiation for functionalization of 2-(2,4-dihalophenyl)-1,3-dithiane derivatives
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Regioselective lithiation followed by functionalization of 2-(2,4-dihalophenyl)-1,3-dithiane derivatives with different electrophiles was achieved in good to excellent yields. When the title compound is treated with n-butyl lithium, lithiation occurs selectively at the aromatic carbon having less acidic proton despite the presence of thermodynamically more acidic 1,3-dithiane proton in the same molecule. Computationally calculated pKa values of the available reactive site protons and the experimental results suggest that the regioselective lithiation in 2-(2,4-dihalophenyl)-1,3-dithiane derivatives is not governed by thermodynamic acidity rather exclusively dictated by the kinetic removal of protons due to cooperative coordination (complex induced proximity effect, CIPE) and inductive effects of the 1,3-dihalo substituents present in the aromatic ring. By employing this regioselective functionalization, diverse 1,2,3,4-tetra-substituted aromatic compounds were prepared with ease.
- Sakthivel, Shanmugam,Kothapalli, Raveendra Babu,Balamurugan, Rengarajan
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p. 1670 - 1679
(2016/02/09)
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- A sustainable multicomponent pyrimidine synthesis
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Since alcohols are accessible from indigestible biomass (lignocellulose), the development of novel preferentially catalytic reactions in which alcohols are converted into important classes of fine chemicals is a central topic of sustainable synthesis. Multicomponent reactions are especially attractive in organic chemistry as they allow the synthesis of large libraries of diversely functionalized products in a short time when run in a combinatorial fashion. Herein, we report a novel, regioselective, iridium-catalyzed multicomponent synthesis of pyrimidines from amidines and up to three (different) alcohols. This reaction proceeds via a sequence of condensation and dehydrogenation steps which give rise to selective C-C and C-N bond formations. While the condensation steps deoxygenate the alcohol components, the dehydrogenations lead to aromatization. Two equiv of hydrogen and water are liberated in the course of the reactions. PN5P-Ir-pincer complexes, recently developed in our laboratory, catalyze this sustainable multicomponent process most efficiently. A total of 38 different pyrimidines were synthesized in isolated yields of up to 93%. Strong points of the new protocol are its regioselectivity and thus the immediate access to pyrimidines that are highly and unsymmetrically decorated with alkyl or aryl substituents. The combination of this novel protocol with established methods for converting alcohols to nitriles now allows to selectively assemble pyrimidines from four alcohol building blocks and 2 equiv of ammonia.
- Deibl, Nicklas,Ament, Kevin,Kempe, Rhett
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supporting information
p. 12804 - 12807
(2015/10/28)
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- The carbonyl group tuned electron-deficient phosphorus ligands and their application in Rhodium catalyzed arylation to aldehydes
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Acylphosphines, which could be efficiently prepared from acid chlorides and secondary phosphines, were developed as a type of carbonyl group tuned electron-deficient phosphorus ligand. They were found to be a kind of efficient ligand in Rhodium catalyzed arylation to aldehydes through accelerating the transmetalation process. Chiral acylphosphine ligands could be generated from carboxylic acids bearing the chiral framework correspondingly.
- Yang, Jiefang,Chen, Xingyu,Wang, Zhiqian
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supporting information
p. 5673 - 5675
(2015/09/15)
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- A versatile and one-pot strategy to synthesize ?±-amino ketones from benzylic secondary alcohols using N -bromosuccinimide
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A metal-free one-pot strategy has been developed for the first time to synthesize pharmaceutically important ?±-amino ketones from readily available benzylic secondary alcohols and amines using N-bromosuccinimide. This new reaction proceeds via three consecutive steps involving oxidation of alcohols, ?±-bromination of ketones, and nucleophilic substitution of ?±-bromo ketones to give ?±-amino ketones. Importantly, this novel one-pot greener reaction avoids direct usage of toxic and corrosive bromine. This methodology has been employed efficiently to synthesize pharmaceutically important amfepramone and pyrovalerone in a single step.
- Guha, Somraj,Rajeshkumar, Venkatachalam,Kotha, Surya Srinivas,Sekar, Govindasamy
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supporting information
p. 406 - 409
(2015/03/04)
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- Tandem α-Alkylation/Asymmetric Transfer Hydrogenation of Acetophenones with Primary Alcohols
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Tandem α-alkylation/asymmetric transfer hydrogenation of acetophenones with primary alcohols, mediated by a single ruthenium catalyst, is described. Under optimized reaction conditions and with use of [Ru(p-cymene)Cl2]2 in combination with an amino acid hydroxyamide ligand, the chiral secondary alcohol products were isolated in moderate yields and in moderate to good enantiomeric excess (up to 89 % ee). One catalyst - one pot - two reactions. Acetophenones are initially alkylated with primary alcohols by the borrowing hydrogen methodology. The alkylation products are directly converted to enantiomerically enriched secondary alcohols.
- Kovalenko, Oleksandr O.,Lundberg, Helena,Hübner, Dennis,Adolfsson, Hans
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supporting information
p. 6639 - 6642
(2016/02/19)
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- Paradigm shift from alkaline (earth) metals to early transition metals in fluoroorganometal chemistry: Perfluoroalkyl titanocene(III) reagents prepared via not titanocene(II) but titanocene(III) species
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Perfluoroalkyl (RF) titanocene reagents [Cp2Ti IIIRF] synthesized via [Cp2TiIIICl] rather than [Cp2TiII] show new types of perfluoroalkylation reactions. The [Cp2TiIIIRF] reagents exhibit a wide variety of reactivity with carbonyl compounds including esters and nitriles, and selectivities far higher than those reported for conventional RFLi and RFMgX reagents. Copyright
- Fujiu, Motohiro,Hashimoto, Ryota,Nakamura, Yuzo,Aikawa, Kohsuke,Ito, Shigekazu,Mikami, Koichi
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supporting information
p. 2382 - 2386
(2014/03/21)
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- A catalytic system for the activation of diorganozinc reagents
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We report a novel catalytic system for the activation of diorganozinc reagents. We assumed that the nucleophilic activation of diethylzinc should be efficiently performed by simple alkali metal salts. Indeed, the combination of sodium salts and 15-crown-5 significantly accelerates the rate of diethylzinc addition to benzaldehyde under mild conditions. The activity of the catalytic system strongly depends on the nature of the anion, decreasing in the order I->Br->Cl->F-. Under the optimized reaction conditions, various aryl, hetero aryl, and aliphatic aldehydes were converted with diethylzinc and the corresponding product was obtained in excellent yields. The first X-ray absorption spectroscopy measurements on such type of reactions provide initial insights that support the proposed catalytic cycle and suggest the formation of a zincate complex.
- Werner, Thomas,Bauer, Matthias,Riahi, Abdol Majid,Schramm, Heiko
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p. 4876 - 4883
(2014/08/05)
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- Robust eco-friendly protocol for the preparation of γ-hydroxy- α,β-acetylenic esters by sequential one-pot elimination-addition of 2-bromoacrylates to aldehydes promoted by LTMP in 2-MeTHF
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An efficient and widely applicable preparation of γ-hydroxy-α, β-acetylenic esters is described by means of a one-pot dehydrobromination of a 2-bromoacrylate ester with LTMP followed by the electrophilic addition of the transient propiolate to different aldehydes in the eco-friendly solvent 2-MeTHF. The Royal Society of Chemistry 2012.
- Pace, Vittorio,Castoldi, Laura,Alcantara, Andres R.,Holzer, Wolfgang
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supporting information; experimental part
p. 1859 - 1863
(2012/08/14)
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- Stereoselective benzylic hydroxylation of alkylbenzenes and epoxidation of styrene derivatives catalyzed by the peroxygenase of Agrocybe aegerita
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Here we report on the stereoselective benzylic hydroxylation and C1-C2 epoxidation of alkylbenzenes and styrene derivatives, respectively, by a heme-thiolate peroxygenase (EC 1.11.2.1) from the fungus Agrocybe aegerita. Benzylic hydroxylation led exclusively to the (R)-1-phenylalkanols. For (R)-1-phenylethanol, (R)-1-phenylpropanol and (R)-1-tetralol, the ee reached >99%. For longer chain lengths, the enantiomeric excesses (ee) and total turnover numbers (TTN) decreased while the number of by-products, e.g. 1-phenylketones, increased. Epoxidation of straight chain and cyclic styrene derivatives gave a heterogeneous picture and resulted in moderate to excellent ee values and TTN: e.g., in the case of (1R,2S)-cis-β-methylstyrene oxide formation, an ee >99% and a TTN of 110000 was achieved. Hydroxylation and epoxidation were true peroxygenations, which was demonstrated by the incorporation of 18O from H218O2 into the products. The use of fed-batch devices and varying feeding strategies for the substrate and co-substrate turned out to be a suitable approach to optimize peroxygenase catalysis.
- Kluge, Martin,Ullrich, Rene,Scheibner, Katrin,Hofrichter, Martin
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supporting information; experimental part
p. 440 - 446
(2012/04/10)
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- Catalytic asymmetric addition of alkyllithium reagents to aromatic aldehydes
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Herein, we report the first efficient catalytic system for the asymmetric alkylation of aldehydes with organolithium reagents in the presence of titanium(IV) isopropoxide. A variety of alkyllithium reagents can be added to aromatic aldehydes in good yields with high enantioselectivities in a simple one-pot procedure under mild conditions. Herein, we report the first efficient catalytic system for the asymmetric alkylation ofaldehydes with organolithium reagents in the presence of titanium(IV) isopropoxide. A variety of alkyllithium reagents can be added to aromatic aldehydes in good yields with high enantioselectivities in a simple one-pot procedure under mild conditions. Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
- Fernandez-Mateos, Emilio,MacIa, Beatriz,Yus, Miguel
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supporting information; body text
p. 3732 - 3736
(2012/09/21)
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- Oxidative kinetic resolution of racemic secondary alcohols in water with chiral PNNP/Ir catalyst
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Using water as solvent, the oxidative kinetic resolution of a wide range of racemic secondary alcohols with a chiral PNNP/Ir catalyst was investigated. The catalytic reaction proceeded smoothly with excellent enantioselectivity (up to 97% ee) under mild conditions, providing an environmentally benign process to achieve optically active alcohols.
- Zhang, Juanni,Yang, Xiangren,Zhou, Han,Li, Yanyun,Dong, Zhenrong,Gao, Jingxing
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supporting information; body text
p. 1289 - 1292
(2012/06/18)
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- A novel one-pot synthesis of secondary alcohols from esters
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Alkylation or vinylation by using organometallic reagents after partial reduction of carboxylic esters with LDBBA gave secondary alcohols, also involving allyl alcohols, without any isolation of intermediates in good yield (54-78%).
- Chae, Min Jung,Jeon, Ah Ram,Park, Jae Kyo,An, Duk Keun
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experimental part
p. 1718 - 1720
(2011/04/25)
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- Generation of carbanions through stibine-metal and bismuthine-metal exchange reactions and its applications to precision synthesis of ω-end-functionalized polymers
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Generation of carbanions from organostibines and organobismuthines through heteroatom-metal exchange reactions was examined from synthetic and mechanistic viewpoints. The exchange reaction proceeded spontaneously upon treatment with various organometallic reagents, such as alkyl lithiums, tetraalkyl zincates, and alkyl magnesium halides to afford the corresponding carbanions quantitatively. Due to the high reactivity of these heteroatom compounds, the exchange reactions took place exclusively even in the presence of various polar functional groups, which potentially react with organometallic species. The advantage of this method was exemplified by the end-group transformation of living polymers that bear these heteroatom species at the ω-polymer end, prepared by using organostibine and bismuthine-mediated living radical polymerizations. Various polymers that bear polar functional groups and acidic hydrogen-for example, poly(methyl methacrylate), poly(butyl acrylate), poly(N-isopropyl acrylamide), and poly(2-hydroxyethyl methacrylate)-could be used in the exchange reactions, and subsequent trapping with electrophiles afforded the corresponding polymers with controlled molecular weights, molecular weight distributions, and end-group functionalities. Competition experiments showed that organostibines and organobismuthines were among the most reactive heteroatom compounds towards organometallic reagents and that their high reactivity was responsible for the high chemoselectivity in the exchange reaction. All's well that ends well: The generation of carbanions from organostibine and -bismuthine compounds was achieved thorough a heteroatom-metal exchange reaction (see scheme). The highly chemoselective exchange reaction could be applied to precision synthesis of varieties of ω-end- functionalized polymers that possess a polar functional group.
- Kayahara, Eiichi,Yamada, Hiroto,Yamago, Shigeru
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supporting information; experimental part
p. 5272 - 5280
(2011/06/20)
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- Selective palladium-loaded MIL-101 catalysts
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Palladium nanoparticles (NPs) of different mean particle size have been synthesized in the host structure of the porous coordination polymer (or metal-organic framework: MOF) MIL-101. The metal-organic chemical vapor deposition method was used to load MIL-101 with the Pd precursor complex [(η5-C5H5)Pd(η3-C 3H5)]. Loadings higher than 50 wt.% could be accomplished. Reduction of the Pd precursor complex with H2 gave rise to Pd NPs inside the MIL-101 (Pd@MIL-101). The reduction conditions, especially the temperature, allows us to make size-conform (size of the Pd NPs correlates with the size of the cavities of the host structure of MIL-101) and undersized Pd NPs. The Pd@MIL-101 samples were characterized by X-ray diffraction, IR spectroscopy, Brauner-Emmett-Teller (BET) analysis, elemental analysis, and transmission electron microscopy (TEM). Catalytic studies, hydrogenation of ketones, were performed with selected Pd@MIL-101 catalysts. Activity, selectivity, and recyclability of the catalyst family are discussed.
- Hermannsdoerfer, Justus,Kempe, Rhett
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experimental part
p. 8071 - 8077
(2011/09/12)
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- Phosphonium salt catalyzed addition of diethylzinc to aldehydes
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The addition of diethylzinc to aromatic, heteroaromatic, and aliphatic aldehydes at room temperature is efficiently catalyzed by 1-7 mol% tetrabutylphosphonium chloride. The corresponding addition products are obtained in good to excellent yields of up to 99%. Moreover, polymer bond phosphonium salts can be used to catalyze this reaction with excellent recovery of the polymer bond catalyst up to three cycles. The application of chiral bifunctional phosphonium salts revealed a remarkable counter anion effect. Changing the anion, the activity of the tetrabutylphosphonium salt decreased in the order Cl- > Br- > I- ≈ TsO- > BF4- ≈ PF6-. However, the nature of the cation had also significant influence. Tetraalkyl-ammonium chlorides showed similar activity compared to phosphonium chlorides, while alkaline metal chlorides proved to be considerably less active. Georg Thieme Verlag Stuttgart.
- Werner, Thomas,Riahi, Abdol Majid,Schramm, Heiko
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supporting information; experimental part
p. 3482 - 3490
(2011/12/04)
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- Versatile zirconium reductants and carbon-carbon coupling agents selectively accessible from the 2:1 molar aggregate of n-butyllithium and zirconium(IV) salts
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In previous studies of transition metal alkyls the 2:1 molar aggregate of n-butyllithium and zirconium(IV) salts has been found to react both with benzylic hydrocarbons and aromatic carbonyl derivatives in diverse and useful ways. In the present study the reactions of the aggregates, 2nBuLi· ZrE4 (E = Cl, OEt), with benzaldehyde have involved carbometallation, hydrometallation and reductive dimerization (paths 1-3) in THF and were selectively achievable by temperature control alone. First, at -78 °C benzaldehyde underwent carbolithiation to give upon hydrolysis 1-phenyl-1-pentanol. However, short-term reaction times and prompt D 2O quenching revealed that with Zr(OEt)4 both benzaldehyde and 1-phenyl-1-pentanol were deuteriated, consistent with the presence of a phenyl(lithioxy)carbene intermediate. The observed dimerization of benzaldehyde to benzyl benzoate by lithium 2,2,6,6-tetramethylpiperidide is also consistent with such a phenyl(lithioxy)carbene intermediate. Second, at 25 °C the 2nBuLi·ZrE4 aggregate reduced benzaldehyde exclusively to benzyl alcohol, which observation is consistent with the formation of the hydrozirconating agent, H2ZrE2. Third, heating the aggregate at reflux and subsequent reaction with benzaldehyde produced solely the reduced dimer, 1,2-diphenyl-1,2-ethanediol with high stereoselectivity: E = Cl, rac/meso of 93:7 and E = OEt, rac/meso of 100:0. The proposed mechanism involves the formation of ZrE2, the epizirconation of benzaldehyde and the insertion of the second benzaldehyde into the zirconaoxacyclopropane under steric control. Finally, the high selectivity in hydrozirconation and reductive dimerization shown by 2nBuLi·ZrE4 appears at this time to be superior to that attainable with analogous titanium or hafnium aggregates. The aggregate 2 nBuLi·ZrE4 (E = Cl, OEt) in THF undergoes highly selective reactions with benzaldehyde controllable by temperature: 1) at -78 °C carbolithiation gives 1-phenyl-1-pentanol; 2) at 25 °C benzyl alcohol is exclusively formed; and 3) after reflux reductive dimerization to the glycol by ZrE2 takes place with high selectivity (rac/meso ≈ 95:5). Copyright
- Eisch, John J.,Gitua, John N.,Yu, Kun
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experimental part
p. 3523 - 3530
(2011/09/15)
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- Vanadium-catalyzed atmosphericoxidation of benzyl alcoholsusing water as Solvent
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A vanadium complex combined with 4,4'-di-tert-butyl-2,2'- bipyridyl as a ligand exhibited excellent catalytic activity in atmosphericoxidation of benzhydrolsusing water as solvent to afford benzophenones in good yields.
- Kodama, Shintaro,Hashidate, Suguru,Nomoto, Akihiro,Yano, Shigenobu,Ueshima, Michio,Ogawa, Akiya
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supporting information; experimental part
p. 495 - 497
(2011/08/05)
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- MPV reduction using AlIII-calix[4]arene Lewis acid catalysts: Molecular-level insight into effect of ketone binding
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Catalytic Meerwein-Ponndorf-Verley (MPV) reduction using Al III-calix[4]arene complexes is investigated as a model system that requires the bringing together of two different chemical species, ketone and alkoxide, within a six-membered transition state. Two-point versus one-point ketone binding is demonstrated to be the most salient feature that controls MPV catalysis rate. A 7.7-fold increase in rate is observed when comparing reactants consisting of a bidentate Cl-containing ketone and sterically and electronically similar but looser-binding ketones, which are substituted with H and F. The one-point and two-point nature of ketone binding for the various ketones investigated is independently assessed using a combination of structural data derived from single-crystal X-ray diffraction and DFT-based molecular modeling. Using MPV catalysis with inherently chiral calix[4]arenes, the effect of multiple point reactant binding on enantioselectivity is elucidated. A higher denticity of ketone binding appears to increase the sensitivity of the interplay between chiral active site structure and MPV reduction enantioselectivity.
- Nandi, Partha,Matvieiev, Yuriy I.,Boyko, Vyacheslav I.,Durkin, Kathleen A.,Kalchenko, Vitaly I.,Katz, Alexander
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experimental part
p. 42 - 49
(2011/12/13)
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- Highly efficient redox isomerization of allylic alcohols and transfer hydrogenation of ketones and aldehydes catalyzed by ruthenium complexes
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A dicationic dichloro-bipyridine-ruthenium complex shows very high catalytic activity in redox isomerization of allylic alcohols but a relatively low one in transfer hydrogenation of ketones; surprisingly, the analogous dimethyl-bipyridine-ruthenium complex shows reverse catalytic activities in the two reactions.
- Liu, Pei Nian,Ju, Kun Dong,Lau, Chak Po
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supporting information; experimental part
p. 275 - 280
(2011/04/16)
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- Palladium-catalyzed asymmetric hydrogenation of simple ketones activated by Br?nsted acids
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Homogeneous Pd(OCOCF3)2/(R)-C4-TunePhos has been successfully applied in the asymmetric hydrogenation of simple ketones activated by catalytic amount of Br?nsted acid with up to 88% ee.
- Zhou, Xiao-Yu,Wang, Duo-Sheng,Bao, Ming,Zhou, Yong-Gui
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supporting information; experimental part
p. 2826 - 2829
(2011/06/21)
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- The generation of palladium silicide nanoalloy particles in a SiCN matrix and their catalytic applications
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The synthesis, characterization and catalytic studies of single phase palladium silicide nanoalloy particles supported by a polymer derived, non-oxide SiCN matrix (Pd2Si@SiCN) are reported. Simultaneous chemical modification of a polyorganosilazane as well as its cross-linking was achieved by the use of an aminopyridinato palladium complex at room temperature. Cross-linking takes place with an evolution of hydrogen and increases the ceramic yield by the retention of carbon and nitrogen atoms. Liberation of ligand, as confirmed by 1H NMR spectroscopy, provides indirect evidence of the transfer of palladium to the nitrogen functions producing metal modified polyorganosilazane whose pyrolysis at 1100 °C under nitrogen atmosphere provides Pd2Si@SiCN. Powder X-ray diffraction (PXRD) studies confirmed the presence of the hexagonal Pd2Si phase in the amorphous SiCN matrix. The size of the particles formed seems to depend upon the nature of the solvent used in the cross-linking step. The amount of palladium complex added seems not to affect the size of particles formed but does increase their population density. Pd2Si@SiCN catalysts were found active for the hydrogenation of ketones. The selectivity of the reaction towards the alcoholic product remains very high. The conversion of the reaction however decreases both with increase in alkyl chain length as well as its branching at alpha carbon. The recyclable Pd2Si@SiCN could be a suitable choice for catalytic transformations under a harsh chemical environment and at higher temperatures.
- Zaheer, Muhammad,Motz, Guenter,Kempe, Rhett
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experimental part
p. 18825 - 18831
(2012/04/10)
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