- MACROCYCLIC COMPOUNDS USEFUL AS CHITINASE INHIBITORS
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The present invention relates to macrocyclic compounds of formula (I) and their use as chitinase inhibitors as well as to pharmaceutical compositions and methods of preparation thereof. The compounds can in particular be used in the treatment, prevention and/or amelioration of asthma.
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Paragraph 0128; 0165-0166
(2021/07/29)
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- Pd(II)-Catalyzed Synthesis of Benzocyclobutenes by β-Methylene-Selective C(sp3)-H Arylation with a Transient Directing Group
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Methylene-selective C-H functionalization is a significant hurdle that remains to be addressed in the field of Pd(II) catalysis. We report a Pd(II)-catalyzed synthesis of benzocyclobutenes by methylene-selective C(sp3)-H arylation of ketones. The reaction utilizes glycine as a transient directing group and a 2-pyridone ligand, which may govern the methylene selectivity by making intimate molecular associations with the substrate during concerted metalation-deprotonation. This reaction is shown to be highly selective for intramolecular methylene C(sp3)-H arylation, thus enabling sequential C(sp3)-H functionalization.
- Chen, Xiangyang,Hoskin, John F.,Houk, K. N.,Provencher, Philip A.,Sorensen, Erik J.,Wong, Jonathan J.,Yu, Jin-Quan
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supporting information
p. 20035 - 20041
(2021/12/09)
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- A General Method for Photocatalytic Decarboxylative Hydroxylation of Carboxylic Acids
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A general and practical method for decarboxylative hydroxylation of carboxylic acids was developed through visible light-induced photocatalysis using molecular oxygen as the green oxidant. The addition of NaBH4 to in situ reduce the unstable peroxyl radical intermediate much broadened the substrate scope. Different sp3 carbon-bearing carboxylic acids were successfully employed as substrates, including phenylacetic acid-type substrates, as well as aliphatic carboxylic acids. This transformation worked smoothly on primary, secondary, and tertiary carboxylic acids.
- Khan, Shah Nawaz,Zaman, Muhammad Kashif,Li, Ruining,Sun, Zhankui
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p. 5019 - 5026
(2020/05/01)
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- KMnO4-catalyzed chemoselective deprotection of acetate and controllable deacetylation-oxidation in one pot
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A novel and efficient protocol for chemoselective deacetylation under ambient conditions was developed using catalytic KMnO4. The stoichiometric use of KMnO4 highlighted the dual role of a heterogeneous oxidant enabling direct access to aromatic aldehydes in one-pot sequential deacetylation-oxidation. The reaction employed an alternative solvent system and allowed the clean transformation of benzyl acetate to sensitive aldehyde in a single step while preventing over-oxidation to acids. Use of inexpensive and readily accessible KMnO4 as an environmentally benign reagent and the ease of the reaction operation were particularly attractive, and enabled the controlled oxidation and facile cleavage of acetate in a preceding step. This journal is
- Gurawa, Aakanksha,Kumar, Manoj,Rao, Dodla S.,Kashyap, Sudhir
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supporting information
p. 16702 - 16707
(2020/10/27)
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- One-Pot Synthesis and Conformational Analysis of Six-Membered Cyclic Iodonium Salts
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Two one-pot procedures for the construction of carbon-bridged diaryliodonium triflates and tetrafluoroborates are described. Strong Br?nsted acids enable the effective Friedel-Crafts alkylation with diversely substituted o-iodobenzyl alcohol derivatives, providing diphenylmethane scaffolds, which are subsequently oxidized and cyclized to the corresponding dibenzo[b,e]iodininium salts. Based on NMR investigations and density functional theory (DFT) calculations, we could verify the so-far-undescribed existence of two stable isomers in cyclic iodonium salts substituted with aliphatic side chains in the carbon bridge.
- Caspers, Lucien D.,Spils, Julian,Damrath, Mattis,Lork, Enno,Nachtsheim, Boris J.
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p. 9161 - 9178
(2020/08/14)
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- Iodolopyrazolium Salts: Synthesis, Derivatizations, and Applications
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The synthesis of iodolopyrazolium triflates via an oxidative cyclization of 3-(2-iodophenyl)-1H-pyrazoles is described. The reaction is characterized by a broad substrate scope, and various applications of these novel cyclic iodolium salts acting as useful synthetic intermediates are demonstrated, in particular in site-selective ring openings. This was finally applied to generate derivatives of the anti-inflammatory drug celecoxib. Their application as highly active halogen-bond donors is shown as well.
- Boelke, Andreas,Caspers, Lucien D.,Kuczmera, Thomas J.,Lork, Enno,Nachtsheim, Boris J.
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supporting information
p. 7261 - 7266
(2020/10/05)
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- Nickel-Catalyzed Asymmetric Reductive 1,2-Carboamination of Unactivated Alkenes
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Starting from diverse alkene-tethered aryl iodides and O-benzoyl-hydroxylamines, the enantioselective reductive cross-electrophilic 1,2-carboamination of unactivated alkenes was achieved using a chiral pyrox/nickel complex as the catalyst. This mild, modular, and practical protocol provides rapid access to a variety of β-chiral amines with an enantioenriched aryl-substituted quaternary carbon center in good yields and with excellent enantioselectivities. This process reveals a complementary regioselectivity when compared to Pd and Cu catalysis.
- He, Jun,Xue, Yuhang,Han, Bo,Zhang, Chunzhu,Wang, You,Zhu, Shaolin
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supporting information
p. 2328 - 2332
(2020/01/08)
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- Selective Hydroboration of Carboxylic Acids with a Homogeneous Manganese Catalyst
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Catalytic reduction of carboxylic acid to the corresponding alcohol is a challenging task of great importance for the production of a variety of value-added chemicals. Herein, a manganese-catalyzed chemoselective hydroboration of carboxylic acids has been developed with a high turnover number (>99?000) and turnover frequency (>2000 h-1) at 25 °C. This method displayed tolerance of electronically and sterically differentiated substrates with high chemoselectivity. Importantly, aliphatic long-chain fatty acids, including biomass-derived compounds, can efficiently be reduced. Mechanistic studies revealed that the reaction occurs through the formation of active manganese-hydride species via an insertion and bond metathesis type mechanism.
- Barman, Milan K.,Das, Kuhali,Maji, Biplab
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p. 1570 - 1579
(2019/01/30)
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- Facile reduction of carboxylic acids to primary alcohols under catalyst-free and solvent-free conditions
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We report the development of a facile protocol for the deoxygenative hydroboration of aliphatic and aryl carboxylic acids to afford corresponding primary alcohols under solvent-free and catalyst-free conditions. The reaction proceeds under ambient temperature exhibits good tolerance towards various functional groups and generates quantitative yields. The plausible mechanism involves the formation of Lewis acid-base adducts as well as the liberation of hydrogen gas.
- Harinath, Adimulam,Bhattacharjee, Jayeeta,Panda, Tarun K.
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supporting information
p. 1386 - 1389
(2019/02/05)
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- Storing redox equivalent in the phenalenyl backbone towards catalytic multi-electron reduction
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Storing and transferring electrons for multi-electron reduction processes are considered to be the key steps in various important chemical and biological transformations. In this work, we accomplished multi-electron reduction of a carboxylic acid via a hydrosilylation pathway where a redox-active phenalenyl backbone in Co(PLY-O,O)2(THF)2, stores electrons and plays a preponderant role in the entire process. This reduction proceeds by single electron transfer (SET) from the mono-reduced ligand backbone leading to the cleavage of the Si-H bond. Several important intermediates along the catalytic reduction reaction have been isolated and well characterized to prove that the redox equivalent is stored in the form of a C-H bond in the PLY backbone via a ligand dearomatization process. The ligand's extensive participation in storing a hydride equivalent has been conclusively elucidated via a deuterium labelling experiment. This is a rare example where the ligand orchestrates the multielectron reduction process leaving only the metal to maintain the conformational requirements and fine tunes the electronics of the catalyst.
- Bhunia, Mrinal,Sahoo, Sumeet Ranjan,Shaw, Bikash Kumar,Vaidya, Shefali,Pariyar, Anand,Vijaykumar, Gonela,Adhikari, Debashis,Mandal, Swadhin K.
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p. 7433 - 7441
(2019/08/15)
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- Regioselectivity Influences in Platinum-Catalyzed Intramolecular Alkyne O-H and N-H Additions
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The steric and electronic drivers of regioselectivity in platinum-catalyzed intramolecular hydroalkoxylation are elucidated. A branch point is found that divides the process between 5-exo and 6-endo selective processes, and enol ethers can be accessed in good yields for both oxygen heterocycles. The main influence arises from an electronic effect, where the alkyne substituent induces a polarization of the alkyne that leads to preferential heteroatom attack at the more electron-deficient carbon. The electronic effects are studied in other contexts, including hydroacyloxylation and hydroamination, and similar trends in directionality are predominant although not uniformly observed.
- Costello, Jeff P.,Ferreira, Eric M.
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supporting information
p. 9934 - 9939
(2019/12/24)
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- N-Heterocycle-Stabilized Iodanes: From Structure to Reactivity
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Pseudocyclic aryl-λ3-iodanes are superior reagents for a variety of oxidative transformations due to a well-balanced relation between stability, solubility and reactivity. Their properties are substantially influenced by a dative interaction between a Lewis base, in general the oxygen atom of a carboxylic acid or an amide, and the central hypervalent iodine atom. This work presents the first systematic investigation of pseudocyclic N-heterocycle-stabilized iodanes (NHIs). The synthesis of these throughout shelf-stable solids is robust and can be achieved on a large scale. Their reactivity is highly tunable, depending on the stabilizing heterocycle. Solid state structures of selected derivatives are reported and their reactivity in a model oxygen transfer reaction is compared. Further derivatization reactions to N-heterocycle-stabilized pseudocyclic diaryliodonium salts and cyclic iodoso species are presented as well.
- Boelke, Andreas,Lork, Enno,Nachtsheim, Boris J.
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p. 18653 - 18657
(2018/11/23)
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- Methanol as hydrogen source: Transfer hydrogenation of aromatic aldehydes with a rhodacycle
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A cyclometalated rhodium complex has been shown to perform highly selective and efficient reduction of aldehydes, deriving the hydrogen from methanol. With methanol as both the solvent and hydrogen donor under mild conditions and an open atmosphere, a wide range of aromatic aldehydes were reduced to the corresponding alcohols, without affecting other functional groups.
- Aboo, Ahmed H.,Bennett, Elliot L.,Deeprose, Mark,Robertson, Craig M.,Iggo, Jonathan A.,Xiao, Jianliang
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supporting information
p. 11805 - 11808
(2018/11/10)
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- Palladium-Catalyzed, Norbornene-Mediated, ortho-Amination ipso-Amidation: Sequential C-N Bond Formation
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A palladium-catalyzed, norbornene-mediated ortho- and ipso-C-N bond-forming Catellani reaction is reported. This reaction proceeds through a sequential intermolecular amination followed by intramolecular cyclization of a tethered amide. The products, ortho-aminated dihydroquinolinones, were generated in moderate to good yields and are present in bioactive molecules. This work highlights the challenge of competing intra- vs intermolecular palladium-catalyzed processes.
- Whyte, Andrew,Olson, Maxwell E.,Lautens, Mark
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supporting information
p. 345 - 348
(2018/01/27)
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- Strategy for Overcoming Full Reversibility of Intermolecular Radical Addition to Aldehydes: Tandem C-H and C-O Bonds Cleaving Cyclization of (Phenoxymethyl)arenes with Carbonyls to Benzofurans
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An intermolecular addition of carbon radicals enabled by a cascade radical coupling strategy is developed. It includes an intermolecular alkyl radical addition to a carbonyl group followed by an intramolecular alkoxy radical addition to haloarenes and produces substituted benzofurans in high yields. The radical nature of this reaction is explored by radical trapping experiments and EPR analysis. The mechanism is investigated by KIE experiments and control experiments. This method could provide rapid and practical access to the key intermediate of TAM-16, a safe and potent antibacterial agent for treating tuberculosis, and, therefore, is of great importance for organic synthesis and the pharmaceutical industry.
- Zheng, Hong-Xing,Shan, Xiang-Huan,Qu, Jian-Ping,Kang, Yan-Biao
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supporting information
p. 3310 - 3313
(2018/06/11)
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- Phenanthroline- tBuOK Promoted Intramolecular C-H Arylation of Indoles with ArI under Transition-Metal-Free Conditions
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The first example of phenanthroline-tBuOK promoted intramolecular radical C-H arylation of N-(2-iodobenzyl)indoles without involvement of transition metals has been developed. A variety of substituted 6H-isoindolo [2, 1-a] indoles were prepared by a simple and efficient intramolecular cyclization using 1,10-phenanthroline in the presence of potassium tert-butoxide and chlorobenzene. This strategy provides a fast and versatile access to isoindolo[2,1-a]indole derivatives for the synthesis of pharmaceuticals and organic electroluminescent (EL) materials.
- Shan, Xiang-Huan,Yang, Bo,Zheng, Hong-Xing,Qu, Jian-Ping,Kang, Yan-Biao
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supporting information
p. 7898 - 7901
(2019/01/04)
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- Cooperative interplay between a flexible PNN-Ru(II) complex and a NaBH4 additive in the efficient catalytic hydrogenation of esters
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A catalyst loading of between 0.001-0.05 mol% of the PNN-bearing ruthenium(II) complex [fac-PNN]RuH(PPh3)(CO) (PNN = 8-(2-diphenylphosphinoethyl)amidotrihydroquinoline), in combination with 5 mol% NaBH4, efficiently catalyzes the hydrogenation of esters to their corresponding alcohols under mild pressures of hydrogen. Both aromatic and aliphatic esters can be converted with high values of TON or TOF achievable. Mechanistic investigations using both DFT calculations and labeling experiments highlight the cooperative role of NaBH4 in the catalysis while the catalytically active species has been established as trans-dihydride [mer-PNHN]RuH2(CO) (PNHN = 8-(2-diphenylphosphinoethyl)aminotrihydroquinoline). The stereo-structure of the PNHN-ruthenium species greatly affects the activity of the catalyst, and indeed the cis-dihydride isomer [fac-PNHN]RuH2(CO) is unable to catalyze the hydrogenation of esters until ligand reorganization occurs to give the trans isomer.
- Wang, Zheng,Chen, Xiangyang,Liu, Bo,Liu, Qing-Bin,Solan, Gregory A.,Yang, Xinzheng,Sun, Wen-Hua
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p. 1297 - 1304
(2017/05/05)
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- Base Catalysis Enables Access to α,α-Difluoroalkylthioethers
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A nucleophilic addition reaction of aryl thiols to readily available β,β-difluorostyrenes provides α,α-difluoroalkylthioethers. The reaction proceeds through an unstable anionic intermediate, prone to eliminate fluoride and generate α-fluorovinylthioethers. However, the use of base catalysis overcomes the facile β-fluoride elimination, generating α,α-difluoroalkylthioethers in excellent yields and selectivities.
- Orsi, Douglas L.,Easley, Brandon J.,Lick, Ashley M.,Altman, Ryan A.
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supporting information
p. 1570 - 1573
(2017/04/13)
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- Method for preparing alcohol through catalytic hydrogenation reduction of carboxylate
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The invention discloses a method for preparing alcohol through catalytic hydrogenation reduction of a carboxylate compound with 2-(diphenylphosphinoethyl)-(5,6,7,8-tetrahydroquinolyl)amine as a ruthenium complex catalyst of ligand. The catalyst has high-efficiency catalysis activity on alkyl benzoate, aromatic esters and fatty esters. The preparation method is simple and has good stability, the catalysis activity of the catalyst is high, and the dosage of the catalyst is 0.025-0.005% of the mole of a substrate. The method can be used for producing alcohols, and has the advantages of simplicity, small pollution to environment, high yield and low cost. Most of carboxylate can be hydrogenated and reduced to form alcohols by using a complex represented by formula (1) with sodium borohydride as an additive, and the conversion number TOC can reach 50000; and a cocaalyst sodium borohydride is used to substitute most of alcoholic alkalis used as a catalyst in especially used in aromatic esters with electron-withdrawing substituent, so the cost is reduced, operation is simple, and industrial production is easy.
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Paragraph 0023; 0027; 0040
(2016/12/07)
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- Chelating Bis(1,2,3-triazol-5-ylidene) Rhodium Complexes: Versatile Catalysts for Hydrosilylation Reactions
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NHC-rhodium complexes (NHC=N-heterocyclic carbenes) have been widely used as efficient catalysts for hydrosilylation reactions. However, the substrates were mostly limited to reactive carbonyl compounds (aldehydes and ketones) or carbon-carbon multiple bonds. Here, we describe the application of newly-developed chelating bis(tzNHC)-rhodium complexes (tz=1,2,3-triazol-5-ylidene) for several reductive transformations. With these catalysts, the formal reductive methylation of amines using carbon dioxide, the hydrosilylation of amides and carboxylic acids, and the reductive alkylation of amines using carboxylic acids have been achieved under mild reaction conditions.
- Nguyen, Thanh V. Q.,Yoo, Woo-Jin,Kobayashi, Shu
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supporting information
p. 452 - 458
(2016/02/12)
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- Intramolecular Pd-Catalyzed Arylation of 1-Amidosugars: A New Route to N-Glycosyl Quinolin-2-ones
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The synthesis of N-glycosylated quinolin-2-ones via an intramolecular N-arylation of glycosylamides is reported. The coupling involves the use of only Pd(OAc)2 as the catalyst and nBu4NOAc as the base in 1,4-dioxane. This versatile approach allows the synthesis of various N-glycosylated quinolin-2-ones with exclusive α or β selectivity.
- Luong, Thi Thanh Huyen,Brion, Jean-Daniel,Lescop, Ewen,Alami, Mouad,Messaoudi, Samir
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supporting information
p. 2126 - 2129
(2016/06/01)
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- Lewis Acid Catalyzed Formal Intramolecular [3 + 3] Cross-Cycloaddition of Cyclopropane 1,1-Diesters for Construction of Benzobicyclo[2.2.2]octane Skeletons
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A novel Lewis acid catalyzed formal intramolecular [3 + 3] cross-cycloaddition (IMCC) of cyclopropane 1,1-diesters has been successfully developed. This supplies an efficient and conceptually new strategy for construction of bridged bicyclo[2.2.2]octane skeletons. This [3 + 3]IMCC could be run up to gram scale and from easily prepared starting materials. This [3 + 3]IMCC, together with our previously reported [3 + 2]IMCC strategy, can afford either the bicyclo[2.2.2]octane or bicyclo[3.2.1]octane skeletons from the similar starting materials by regulating the substituents on vinyl group.
- Ma, Weiwei,Fang, Jie,Ren, Jun,Wang, Zhongwen
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p. 4180 - 4183
(2015/09/15)
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- A monolith immobilised iridium Cp catalyst for hydrogen transfer reactions under flow conditions
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An immobilised iridium hydrogen transfer catalyst has been developed for use in flow based processing by incorporation of a ligand into a porous polymeric monolithic flow reactor. The monolithic construct has been used for several redox reductions demonstrating excellent recyclability, good turnover numbers and high chemical stability giving negligible metal leaching over extended periods of use.
- Rojo, Maria Victoria,Guetzoyan, Lucie,Baxendale, Ian. R.
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p. 1768 - 1777
(2015/02/19)
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- Pinpoint-fluorinated phenacenes: New synthesis and solubility enhancement strategies
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The Pd(II)-catalyzed cyclizations of 2,2-difluorovinylated biaryls, following a Friedel-Crafts-type mechanism, provide a new route to pinpoint-fluorinated phenacenes. The single fluorine substituent stabilized the synthesized fluoropicenes (fluoro[5]phenacenes) toward aerial oxidation and contributed to their solubility in organic solvents. For example, 6- and 13-fluoropicenes were 25- and 15-fold more soluble in THF than nonfluorinated picene. X-ray crystal structure analysis revealed that the fluorine substituent did not alter molecular planarity.
- Fuchibe, Kohei,Morikawa, Toshiyuki,Shigeno, Kento,Fujita, Takeshi,Ichikawa, Junji
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supporting information
p. 1126 - 1129
(2015/03/14)
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- Pinpoint-fluorinated phenanthrene synthesis based on C-F bond activation of difluoroalkenes Dedicated to Prof. Véronique Gouverneur on the occasion of her receipt of the 2014 ACS Award for Creative Work in Fluorine Chemistry.
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Treatment with a cationic palladium(II) catalyst promoted the Friedel-Crafts-type cyclization of 1,1-difluoro-1-alkenes bearing a biphenyl skeleton to afford regioselectively fluorinated (pinpoint-fluorinated) phenanthrenes via C-F bond activation. The obtained pinpoint-fluorinated phenanthrenes were observed to be organized by π-π and C-H?F interactions to exhibit columnar and layer structures in the solid state.
- Fuchibe, Kohei,Morikawa, Toshiyuki,Ueda, Ryu,Okauchi, Tatsuo,Ichikawa, Junji
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supporting information
p. 106 - 115
(2015/11/10)
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- Synthesis and characterization of fluorescent-active triazole-gold complexes
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Fluorescence active fused-triazole was developed as a ligand in gold(I) cation coordination. The coordination ability was evaluated using NMR and fluorescence emission. Our previously reported N-2-aryl-triazoles, though gave good emission, could not form stable complexes with gold cations. A new N-fused-triazole (NFT) derivative was prepared and the ligand indicated good fluorescence emission, and formed strong coordination with gold cations. Both ligand and complex were characterized by X-ray crystallography. Fluorescence properties of various gold complexes (with different primary ligands) were evaluated, which suggested the feasibility of using fluorescence emission as potential tools for future mechanistic investigation.
- Dong, Boliang,Su, Yijin,Ye, Xiaohan,Petersen, Jeffrey L.,Shi, Xiaodong
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p. 1235 - 1238
(2015/08/06)
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- Synthesis of structurally diverse diarylketones through the diarylmethyl sp3 C-H oxidation
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Under open-flask conditions, an efficient method to assemble a series of diversely functionalized diarylketones in the presence of commercially available NBS has been developed. Yields of up to 99% have been achieved employing diarylmethanes as starting material. Based on 18O-labeled experiment, the addition of stoichiometric water eventually leads to excellent yields in all carbonylation cases.
- He, Chao,Zhang, Xiaohui,Huang, Ruofeng,Pan, Jing,Li, Jiaqiang,Ling, Xuege,Xiong, Yan,Zhu, Xiangming
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supporting information
p. 4458 - 4462
(2014/08/05)
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- Synthesis, structure, and catalytic activity of new ruthenium(II) indenylidene complexes bearing unsymmetrical N - heterocyclic carbenes
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New robust and air-stable ruthenium(II) indenylidene type second-generation precatalysts with unsymmetrical N-heterocyclic carbene (NHC) ligands were synthesized. The reaction profiles of these complexes were studied in commercial-grade solvents in air with model substrates leading to the di-, tri-, and tetrasubstituted olefins. In addition, application of selected precatalysts for olefin metathesis reactions on a broad spectrum of substrates with different functional groups was examined. Studies of solvent effects for the selected precatalysts as well as thermal activation of the corresponding complexes showed significant differences in their activities. Observed relationships in connection with single-crystal X-ray analysis revealed the influence of the unsymmetrical NHC ligands on the initiation rate of precatalysts. Dissociation of the phosphine ligand, the rate-determining step for our most active precatalysts, is accelerated by the steric repulsion of the dangling benzyl arm and the tricyclohexylphosphine ligand. A precatalyst with a hemilabile benzyl arm evinced decreased activity, probably due to coordination of the heteroatom to the ruthenium core taking place after dissociation of the phosphine ligand.
- Ablialimov, Osman,Kedziorek, Mariusz,Malinska, Maura,Wozniak, Krzysztof,Grela, Karol
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supporting information
p. 2160 - 2171
(2014/06/09)
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- Solvent-free reduction of carboxylic acids to alcohols with NaBH4 promoted by 2,4,6-trichloro-1,3,5-triazine and PPh3 in the presence of K2CO3
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A simple, rapid, and eco-friendly method for NaBH4 reduction of carboxylic acids to alcohols under solvent-free conditions was developed using a combination of 2,4,6-trichloro-1,3,5-triazine (TCT) with a catalytic amount of triphenylphosphine as an acid activator. With the 1 : 0.2 : 1.5 : 2 mole ratio of TCT : PPh3 : K2CO3 : NaBH4, carboxylic acids including aromatic acids, aliphatic acids, and N-protected α-amino acids (Fmoc, Z) could readily undergo reduction to give the corresponding alcohols in good to excellent yields within 10 min.
- Jaita, Subin,Kaewkum, Pantitra,Duangkamol, Chuthamat,Phakhodee, Wong,Pattarawarapan, Mookda
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p. 46947 - 46950
(2014/12/10)
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- Terminal olefins to chromans, isochromans, and pyrans via allylic C-H oxidation
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The synthesis of chroman, isochroman, and pyran motifs has been accomplished via a combination of Pd(II)/bis-sulfoxide C-H activation and Lewis acid co-catalysis. A wide range of alcohols are found to be competent nucleophiles for the transformation under uniform conditions (catalyst, solvent, temperature). Mechanistic studies suggest that the reaction proceeds via initial C-H activation followed by a novel inner-sphere functionalization pathway. Consistent with this, the reaction shows reactivity trends orthogonal to those of traditional Pd(0)-catalyzed allylic substitutions.
- Ammann, Stephen E.,Rice, Grant T.,White, M. Christina
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supporting information
p. 10834 - 10837
(2014/08/18)
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- Palladium-catalyzed insertion of N-tosylhydrazones for the synthesis of isoindolines
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Isoindolines are synthesized by palladium-catalyzed coupling reaction of N-(2-iodobenzyl) anilines with α,β-unsaturated N-tosylhydrazones. The reaction has several potential advantages: (1) toleration of a wide range of functional groups, (2) easy to handle and with mild conditions, (3) enriches the isoindoline family, (4) two new bonds form in one step.
- Zhou, Ping-Xin,Luo, Jian-Yi,Zhao, Lian-Biao,Ye, Yu-Ying,Liang, Yong-Min
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p. 3254 - 3256
(2013/05/08)
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- Zinc triflate: A mild and efficient catalyst for deprotection of tetrahydropyranyl ethers
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Treatment of tetrahydropyranyl (THP) ethers with zinc triflate in methanol provides a simple and efficient process for deprotection of these ethers and the parent alcohols are obtained in excellent yields.
- Srinivasulu,Satyanarayana,Ravi Kumar
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p. 2419 - 2422
(2014/03/21)
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- Synthesis of benzannulated spiroacetals using chiral gold-phosphine complexes and chiral anions
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The development of an asymmetric gold-catalysed dihydroalkoxylation strategy for the synthesis of the 3′H-spiro[chroman-2,1′- isobenzofuran] spiroacetal ring system 5 is described. Spiroacetal was generated in up to 87:13 enantiomeric ratio using chiral gold-phosphine complexes and chiral silver phosphate Ag(S)-TRIP.
- Quach, Rachelle,Furkert, Daniel P.,Brimble, Margaret A.
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supporting information
p. 5865 - 5868
(2013/10/21)
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- Reactivity of conformationally constrained bispropargyl sulfones: Complete preference for 6π-electrocyclization process
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The reactivity of a series of conformationally constrained bispropargyl sulfones with an ortho alkenyl moiety was studied. Under basic condition, these molecules underwent isomerization, first to monoallene followed by 6π-electrocyclization (6π-EC). Another cycle of isomerization and 6π-EC gave the bis naphthyl sulfones. No Garratt-Braverman (GB) Cyclization product could be isolated even on easing up the strain. Computations with DFT (at BP86-D3/def2-SVP level) indicated that, it is energetically more favorable for the initially formed monoallenic intermediate to undergo electrocyclization rather than isomerize to bisallene. This is in contrast to the acyclic unconstrained counterpart, where isomerization to bisallene is preferred and competing GBC/6π-EC of bisallenes results in mixture of products.
- Ghosh, Debaki,Jana, Saibal,Panja, Arpita,Anoop, Anakuthil,Basak, Amit
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p. 8724 - 8730
(2013/09/23)
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- Simple and efficient method for deprotection of tetrahydropyranyl ethers by using Silica supported sodium hydrogen sulphate
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Tetrahydropyranyl (THP) ethers have been efficiently and simply deprotected by using Silica supported sodium hydrogen sulphate (NaHSO4-SiO 2) in methanol at room temperature to regenerate the parent alcohols in high yields. Tetrahydropyranyl (THP) ethers have been efficiently and simply deprotected by using silica supported sodium hydrogen sulphate (NaHSO 4-SiO2) in methanol at room temperature to regenerate the parent alcohols in high yields.
- Kumar, K. Ravi,Satyanarayana,Reddy, B. Srinivasa
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experimental part
p. 1189 - 1191
(2012/07/27)
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- Indium tri(isopropoxide)-catalyzed selective Meerwein-Ponndorf-Verley reduction of aliphatic and aromatic aldehydes
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Indium tri(isopropoxide)-catalyzed Meerwein-Ponndorf-Verley reduction of aliphatic and aromatic aldehydes in 2-propanol gave selectively the corresponding primary alcohols in good to excellent yields at room temperature. A wide range of functional groups including alkene, ether, ketone, ester, nitrile, and nitro were tolerated under the optimum reaction conditions. Chemoselective reductions were also achieved not only between aromatic aldehyde, aromatic ketone, and epoxide but also between aliphatic aldehyde and alkene.
- Lee, Jaeyoung,Ryu, Taekyu,Park, Sangjune,Lee, Phil Ho
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supporting information; experimental part
p. 4821 - 4825
(2012/07/03)
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- Synthesis and SERCA activities of structurally simplified cyclopiazonic acid analogues
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The indole alkaloid cyclopiazonic acid (CPA) is one of the few known nanomolar inhibitors of sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) besides the anticancer drug thapsigargin and the antiplasmoidal terpenoid artemisinin. Due to its less complex structure CPA represents an attractive lead structure for the development of novel antimalarial drugs or for applications in the field of plant protection. We report here the first syntheses of structurally simplified CPA fragments and discuss their SERCA activities on the basis of published crystal structures of CPA-SERCA complexes.
- Yao, Sheng,Gallenkamp, Daniel,Woelfel, Katharina,Lueke, Bettina,Schindler, Michael,Scherkenbeck, Juergen
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scheme or table
p. 4669 - 4678
(2011/09/12)
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- Aza Hopf cyclization: synthesis and reactivity of cyclic azadieneynes
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Nine- and 10-membered azadieneynes have been synthesized for the first time via an intramolecular aza Wittig reaction. The compounds undergo Hopf cyclization under ambient conditions to the hydroxy dihydroisoquinoline derivatives.
- Mandal, Sayantan,Basak, Amit
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scheme or table
p. 3641 - 3644
(2009/09/30)
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- Brominative indolization of an unsaturated bridgehead sultam with extrusion of sulfur dioxide
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The dissolution of an unsaturated bridgehead sultam in liquid bromine at room temperature results in the formation of a pentabromo indole derivative in an unusual desulfonylative process.
- Preston, Adam J,Paquette, Leo A.
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- Parham-type cycliacylation with Weinreb amides. Application to the synthesis of fused indolizinone systems
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(Matrix presented) Weinreb amides behave as efficient internal electrophiles in Parham-type cycliacylation reactions. Thus, aryl- and heteroaryllithiums generated by lithium-halogen exchange undergo intramolecular cyclization to give fused indolizinone systems as pyrrolo[1,2-b]isoquinolines, thieno[2,3-f]indolizinones, and pyrrolo[1,2-b]acridinones in high yields.
- Ruiz, Javier,Sotomayor, Nuria,Lete, Esther
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p. 1115 - 1117
(2007/10/03)
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- Synthesis of o-Dialkenylbenzenes and Indenes Using Heck and Oxypalladation Reactions
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o-Bromostyrenes 2-Br react with various alkenes in the presence of palladium catalysts to give either substituted indene 6 or o-diethenylbenzene derivatives 3, depending on the reaction conditions.Under oxidative conditions the latter can be cyclized to indene derivatives as well. - Keywords: Cross-coupling, Heck; Palladium catalysis; Indanes; Arenes, dialkenyl-N
- Braese, Stefan,Ruemper, Joerg,Voigt, Katharia,Albecq, Stephane,Thurau, Gert,et al.
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p. 671 - 678
(2007/10/03)
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- Accelerating effect induced by the structure of α-amino acid in the copper-catalyzed coupling reaction of aryl halides with α-amino acids. Synthesis of benzolactam-V8
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The coupling of optically pure α-amino acids with aryl halides produces enantiopure N-aryl-α-amino acids with retention of configuration under the catalysis of CuI. This reaction can complete at much lower temperature than typical Ullmann condensation even for electron-rich aryl halides, which indicates that an accelerating effect induced by the structure of the α- amino acid exists in this reaction. α-Amino acids with larger hydrophobic groups give higher coupling yields, while those with smaller hydrophobic groups only deliver lower yields and no coupling products were detected for those with hydrophilic groups. No racemization was observed in most cases of this coupling reaction. After some controlled experiments, a possible mechanism including the π-complex and the intramolecular substitution reaction is proposed. Based on this catalyzed reaction, a facile and stereoselective synthesis of benzolactam-V8, a new PKC activator, is achieved.
- Ma, Dawei
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p. 12459 - 12467
(2007/10/03)
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- Correlation Analysis of Reactivity in the Oxidation of Substituted Benzyl Alcohols by Pyridinium Hydrobromide Perbromide
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Oxidation of monosubstituted benzyl alcohols by pyridinium hydrobromide perbromide (PHPB) leads to the formation of the corresponding benzaldehydes.The reaction is first order with respect to PHPB.Michaelis-Menten-type kinetics were observed with respect to he alcohol.The oxidation of α,α-dideuteriobenzyl alcohol indicated the presence of a substantial kinetic isotope effect.The rates of oxidation of meta- and para-substituted benzyl alcohols were correlated in terms of Taft's and Swain's dual substituent-parameter equations.The rates of the meta compounds correlated best with Taft's ?1 and ?0R values whereas the para-compounds showed an excellent correlation with Taft's ?1 and ?R + constants.The rates of the otho-substituted alcohols showed very good correlation with Charton's triparametric equation.The rate increased with an increase in the polarity of the solvent.A mechanism involving a rapid reversible formation of an intermediate complex and its subsequent decomposition in the rate-determining step has been proposed.
- Suri, Deepa,Banerji, Kalyan K.,Kothari, Seema
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p. 1734 - 1758
(2007/10/03)
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- Reduction of Aldehyde with Tributyltin Hydride-HMPA Combined System
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Bu3-SnH-HMPA combined system is an efficient reagent for the reduction of aldehydes.The reaction proceeds in good yields, and chemoselective carbonyl reduction is achieved for the substrate which includes another reducible group.Moreover, the intermediate, tin alkoxide, undergoes further reaction such as the preparation of ethers and heterocyclic compounds in the one pot procedure.
- Shibata, Ikuya,Yoshida, Tomoyuki,Baba, Akio,Matsuda, Haruo
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p. 619 - 622
(2007/10/02)
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- The Synthesis of Some Thiophenophanes and Attempted Cyclisations to Polycyclic Thiophenium Salts
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5,10-Diphenylcyclotrideca-2,4,10,12-tetraene-6,8-diyn-1-one (28), 5,6,7,8-tetrahydrodibenzocyclotridecen-15-one (21), and 13,14,16,17-tetrahydro-5,6,7,8-tetradehydrodibenzocyclotridecen-15-one (40) were synthesized.All attempts to add hydrogen sulphide across the triple bonds of these compounds to give thiophenes failed. 13,14,16,17-Tetrahydro-5,8-epithiodibenzocyclotridecen-15-one (43), from which hydrogen sulphide was removed by DDQ or chloroanil to give the ketone (40), was synthesized via the copper(II) acetate oxidation of 1,5-bis(2-ethynylphenyl)pentan-3-one (36).This ketone was obtained from 2-iodobenzaldehyde which on successive treatment with acetone, and ethynyltrimethylsilane yielded 1,5-bis(2-trimethylsilylethynylphenyl)penta-1,4-dien-3-one (18).Tributyltin hydride reduced the vinyl double bonds only in this ketone, and subsequent hydrolysis gave the ketone (36).Reduction of the cyclic ketone (40) with sodium borohydride gave the alcohol (41), sodium sulphide converted the diyne grouping into a thiophene ring giving the thiophene alcohol (42), and chromic acid now yielded the ketone (43).Attempts to convert this alcohol (42) and ketone (43) into pentacyclic sulphonium salts or related compounds resulted in elimination of oxygen and the formation of olefins.
- Acheson, R. Morrin,Lee, Gary C. M.
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p. 2321 - 2332
(2007/10/02)
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- EFFICIENT PALLADIUM-MEDIATED SYNTHESIS OF A SPIROCYCLIC MODEL FOR FREDERICAMYCIN A.
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A palladium-promoted intramolecular arylation of a β-diketone generates a spirocyclic system as a model for Fredericamycin A.
- Ciufolini, Marco A.,Browne, Margaret E.
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p. 171 - 174
(2007/10/02)
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- Direct ortho-Metalation of Benzyl Alcohols. A Novel Method of Preparing ortho-Substituted Benzyl Alcohols
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Benzyl alcohol and other phenylcarbinols (8a - 11a), including α-tetralol (12a), are doubly deprotonated by excess n-butyllithium/TMEDA in pentane to give lithium ortho-lithioalkoxides (2, 8b - 12b).Alkylations (-> 3a - d, table 1), reactions with heteroelectrophiles (-> 3e - k, table 2) and with carbonyl compounds (-> 6, 13 - 17, tables 3 and 4), as well as subsequent reactions of the primary adducts (-> phthalanes 7, table 3) furnish a large variety of ortho-substituted benzyl alcohol derivatives.The scope and limitations of the dilithioorganyls (sections B and C), their mode of formation (section A), and attempts to doubly metalate 2-phenylethanol are discussed.
- Meyer, Norbert,Seebach, Dieter
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p. 1304 - 1319
(2007/10/02)
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