- A general copper-catalyzed radical C(sp3)?C(sp2) cross-coupling to access 1,1-diarylalkanes under ambient conditions
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A general copper-catalyzed C(sp3)?C(sp2) cross-coupling of (hetero)benzyl bromides with the air- and moisture-stable aryl nucleophiles has been developed, providing a facile access to pharmaceutically useful 1,1-di(hetero)arylalkane and 1-aryl-1-heteroarylalkane scaffolds. Critical to the success is the utilization of a proline-based N,N,P-ligand to enhance the reducing capability of copper, thus easily converting benzyl bromides to the corresponding radical species via a single-electron transfer process under ambient conditions. The reaction features a broad substrate scope, covering (hetero)arylboronate esters, oxadiazoles, and benzo[d]oxazoles, as well as primary and secondary (hetero)benzyl bromides with excellent functional group tolerance.
- Su, Xiao-Long,Jiang, Sheng-Peng,Ye, Liu,Xu, Guo-Xing,Chen, Ji-Jun,Gu, Qiang-Shuai,Li, Zhong-Liang,Liu, Xin-Yuan
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supporting information
(2021/05/06)
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- Carbosulfenylation of Alkenes with Organozinc Reagents and Dimethyl(methylthio)sulfonium Trifluoromethanesulfonate
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The electrophilic alkylthiolation of alkenes, initiated by dimethyl(methylthio)sulfonium salts and the subsequent addition of various heteronucleophilies has been well-established. Regarding the use of carbon nucleophiles, however, only carefully designed sp-type carbon sources have been successfully applied. We herein present our findings on the methylthiolation of alkenes with dimethyl(methylthio)sulfonium trifluoromethanesulfonate, followed by carbon-carbon bond formation in the presence of organozinc reagents, thus achieving a catalyst-free protocol toward to the carbosulfenylation of alkenes.
- Tang, Meizhong,Han, Shuxiong,Huang, Shenglan,Huang, Shenlin,Xie, Lan-Gui
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supporting information
p. 9729 - 9734
(2020/12/21)
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- Iron-catalysed enantioconvergent Suzuki-Miyaura cross-coupling to afford enantioenriched 1,1-diarylalkanes
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The first stereoconvergent Suzuki-Miyaura cross-coupling reaction was developed to afford enantioenriched 1,1-diarylalkanes. An iron-based complex containing a chiral cyanobis(oxazoline) ligand framework was best to obtain enantioenriched 1,1-diarylalkanes from cross-coupling reactions between unactivated aryl boronic esters and benzylic chlorides. Enhanced yields were obtained when 1,3,5-trimethoxybenzene was used as an additive, which is hypothesized to extend the lifetime of the iron-based catalyst. Exceptional enantioselectivities were obtained with challenging ortho-substituted benzylic chlorides. This journal is
- Tyrol, Chet C.,Yone, Nang S.,Gallin, Connor F.,Byers, Jeffery A.
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p. 14661 - 14664
(2020/12/02)
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- A Unified Explanation for Chemoselectivity and Stereospecificity of Ni-Catalyzed Kumada and Cross-Electrophile Coupling Reactions of Benzylic Ethers: A Combined Computational and Experimental Study
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Ni-catalyzed C(sp3)-O bond activation provides a useful approach to synthesize enantioenriched products from readily available enantioenriched benzylic alcohol derivatives. The control of stereospecificity is key to the success of these transformations. To elucidate the reversed stereospecificity and chemoselectivity of Ni-catalyzed Kumada and cross-electrophile coupling reactions with benzylic ethers, a combined computational and experimental study is performed to reach a unified mechanistic understanding. Kumada coupling proceeds via a classic cross-coupling mechanism. Initial rate-determining oxidative addition occurs with stereoinversion of the benzylic stereogenic center. Subsequent transmetalation with the Grignard reagent and syn-reductive elimination produce the Kumada coupling product with overall stereoinversion at the benzylic position. The cross-electrophile coupling reaction initiates with the same benzylic C-O bond cleavage and transmetalation to form a common benzylnickel intermediate. However, the presence of the tethered alkyl chloride allows a facile intramolecular SN2 attack by the benzylnickel moiety. This step circumvents the competing Kumada coupling, leading to the excellent chemoselectivity of cross-electrophile coupling. These mechanisms account for the observed stereospecificity of the Kumada and cross-electrophile couplings, providing a rationale for double inversion of the benzylic stereogenic center in cross-electrophile coupling. The improved mechanistic understanding will enable design of stereoselective transformations involving Ni-catalyzed C(sp3)-O bond activation.
- Chen, Pan-Pan,Lucas, Erika L.,Greene, Margaret A.,Zhang, Shuo-Qing,Tollefson, Emily J.,Erickson, Lucas W.,Taylor, Buck L. H.,Jarvo, Elizabeth R.,Hong, Xin
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p. 5835 - 5855
(2019/04/03)
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- Synthesis of 1,1′-diarylethanes and related systems by displacement of trichloroacetimidates with trimethylaluminum
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Benzylic trichloroacetimidates are readily displaced by trimethylaluminum under Lewis acid promoted conditions to provide the corresponding methyl substitution product. This method is a convenient way to access 1,1′-diarylethanes and related systems, which play a significant role in medicinal chemistry, with a number of systems owing their biological activity to this functionality. Most benzylic substrates undergo ready displacement, with electron deficient systems being the exception. The use of an enantiopure imidate showed significant racemization, implicating the formation of a cationic intermediate.
- Mahajani, Nivedita S.,Chisholm, John D.
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p. 4131 - 4139
(2018/04/14)
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- Nickel(0)-Catalyzed Hydroarylation of Styrenes and 1,3-Dienes with Organoboron Compounds
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A Ni-catalyzed hydroarylation of styrenes and 1,3-dienes with organoboron compounds has been developed. The reaction offers a highly selective approach to diarylalkanes and allylarenes under redox-neutral conditions. In this hydroarylation reaction, a new strategy that uses the proton of methanol to generate the active catalyst species Ni?H was developed. The Ni-catalyzed hydroarylation, combined with a Ir-catalyzed C?H borylation, affords a very efficient and straightforward access to a retinoic acid receptor agonist.
- Xiao, Li-Jun,Cheng, Lei,Feng, Wei-Min,Li, Mao-Lin,Xie, Jian-Hua,Zhou, Qi-Lin
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supporting information
p. 461 - 464
(2018/02/21)
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- One-pot reductive coupling reactions of acetyl naphthalene derivatives, tosylhydrazide, with arylboronic acids
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In this study, a one-pot two-step reductive coupling between acetyl naphthalene derivatives, tosylhydrazide, and arylboronic acids, affording substituted 1(or 2)-(1-phenylethyl)naphthalenes in moderate-to-excellent yields, was reported. Notably, solvent played a crucial role in the coupling of 1-acetyl naphthalene derivatives (toluene) or 2-acetyl naphthalene derivatives (1,4-dioxane) as starting materials. Meanwhile, the scope of this one-pot coupling reaction was extended to 1(or 2)-naphthaldehyde substrates. Particularly, the system was also suitable to synthesize 1(or 2)-(1-phenylethyl)naphthalenes on a multi-gram scale, and was applied in the synthesis of naphthylmethyl substituted carbazolyl compounds.
- Shen, Xu,Liu, Ping,Liu, Yang,Liu, Yan,Dai, Bin
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supporting information
p. 785 - 793
(2017/01/16)
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- Aldimine-directed branched-selective hydroarylation of styrenes
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Branching out: A simple and inexpensive cobalt/triarylphosphine catalyst promotes aldimine-directed hydroarylation of styrene with high branched regioselectivity to afford 1,1-diarylethane derivatives in good yields under mild reaction conditions. The ortho-formyl group in the hydroarylation products is amenable to dehydrative cyclization, to give fused polycyclic aromatic hydrocarbons, as well as decarbonylative removal. Copyright
- Lee, Pin-Sheng,Yoshikai, Naohiko
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p. 1240 - 1244
(2013/03/13)
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- Bidentate Lewis acid catalyzed inverse-electron-demand Diels-Alder reaction for the selective functionalization of aldehydes
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The inverse-electron-demand Diels-Alder (IEDDA) reaction catalyzed by a bidentate Lewis acid was applied to enamines generated in situ from aldehydes. In general, a high functional group tolerance has been observed. Side reactions during the enamine forming step can limit the yield of the desired naphthalene. For citronellal as substrate, the initial intermediate after the catalyzed IEDDA reaction was trapped by an intramolecular Diels-Alder reaction to furnish a tricyclic compound. This scaffold represents the framework of natural products such as valerianoids A-C or the patchouli alcohol. Georg Thieme Verlag Stuttgart New York.
- Schweighauser, Luca,Bodoky, Ina,Kessler, Simon N.,Haeussinger, Daniel,Wegner, Hermann A.
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experimental part
p. 2195 - 2199
(2012/09/22)
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- Tin exchanged heteropoly tungstate: An efficient catalyst for benzylation of arenes with benzyl alcohol
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The partial exchange of tin with the protons of 12-tungstophosphoric acid (TPA) results in a highly active heterogeneous catalyst for benzylation of arenes with benzyl alcohol as benzylating agent. The catalysts were characterized by X-ray diffraction, Laser-Raman and FT-IR of pyridine adsorption. The catalytic activity depends significantly on the extent of tin exchanged with the protons of heteropoly tungstate. The characterization results suggest the presence of Lewis acidic sites by the exchange of tin. The catalyst with partial exchange of Sn showed high benzylation activity, which in turn related to variation in acidity of the catalysts. The catalyst is highly active for benzylation reaction irrespective of the nature of substituted arenes and benzyl alcohols. These catalysts are highly active compared to other acid catalysts used for benzylation of different arenes. The catalyst is easy to separate from reaction mixture and exhibit consistent activity upon reuse. The plausible reaction mechanism based on the role of both Lewis and Bronsted acid sites of the catalyst was discussed.
- Ramesh Kumar, Ch.,Rao, K.T. Venkateswara,Sai Prasad,Lingaiah
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experimental part
p. 17 - 24
(2011/04/21)
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- Palladium-catalyzed cross-coupling reaction of secondary benzylic bromides with grignard reagents
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"Chemical Equation Presented" A mild palladium-catalyzed Kumada-Corriu reaction of secondary benzylic bromides with aryl and alkenyl Grignard reagents has been developed. In the presence of the Xantphos ligand, the undesired β-elimination pathway Is minimized, affording the corresponding cross-coupling products In acceptable to good yields. The reaction proceeds with inversion of the configuration.
- Lopez-Perez, Ana,Adrio, Javier,Carretero, Juan C.
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supporting information; experimental part
p. 5514 - 5517
(2010/02/28)
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- Direct benzylic alkylation via Ni-catalyzed selective benzylic sp 3 C-O activation
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This article demonstrates the first cross coupling of benzyl ether with Grignard reagents via Ni-catalyzed benzylic sp3 C-O activation with high efficiency and excellent chemoselectivity. Benzylic sp3 C-O and aryl sp2 C-O were differentiated, controlled by ligands. Copyright
- Guan, Bing-Tao,Xiang, Shi-Kai,Wang, Bi-Qin,Sun, Zuo-Peng,Wang, Yang,Zhao, Ke-Qing,Shi, Zhang-Jie
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p. 3268 - 3269
(2008/10/09)
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- Electrochemical Reduction of 1,1-Diaryl-substituted Ethenes in Dimethylformamide
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The cathodic behaviour of 1,1-diaryl-substituted ethenes (Ar)PhC=CH2 (where Ar=phenyl-, 2-naphthyl-, 2-pyridyl-, 2-thienyl-, 2-furyl-) at a Hg cathode in N,N-dimethylformamide (DMF) and 0.1 mol dm-3 tetraethylammonium tetrafluoroborate (TEAF), was investigated by cyclic voltammetry and controlled potential electrolysis experiments.In cyclic voltammetry, at a potential scan rate of 0.2 V s-1, all substrates showed an irreversible reduction peak p,c) between -2.27 and -2.54 V vs. saturated calomel electrode (SCE)>.Controlled potential coulometries indicated that the apparent charge number of the process involved ranges from 1 to 2.The reduction products were characterised as (Ar)PhCH-Me (1-aryl-1-phenylethanes) and (Ar)PhCH-2-CHPh(Ar) (1,4-diaryl-1,4-diphenylbutanes).The charge number of the process and the ratio between the two different reduction products depended strongly on the structure and concentration of the substrate.Exhaustive electrolyses performed in the presence of variable amounts of D2O or in DMF allowed us to suggest that two distinct pathways are involved in the reduction process, leading to the monomeric and dimeric product, respectively.Hypotheses on the nature of the two reduction mechanisms are discussed.
- Fruianu, Michelina,Marchetti, Mauro,Melloni, Giovanni,Sanna, Gavino,Seeber, Renato
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p. 2039 - 2044
(2007/10/02)
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- Process for improving traction coefficient of traction drive fluid at high temperatures
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A process for improving traction coefficient of traction drive fluid at high temperatures by using a compound represented by the general formulae (I), (II) or (III) as a base stock of traction drive fluid, STR1 (All the symbols are as defined in the appended claims). This process is helpful for reducing the change of traction coefficients over a wide range of from low temperature to high temperature.
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- The addition of simple aromatic hydrocarbons to condensed aromatic thiophenes promoted by aluminum chloride. Part II. Naphthothiophene
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The reaction of naphthothiophene with an aromatic hydrocarbon in the presence of aluminum chloride at 20 deg C gave either a 3-aryl-2,3-dihydronaphthothiophene by addition to the 2,3-bond or 2,3-dihydronaphthothiophene as a result of hydride abstraction.Occasionally 2-aryl-2,3-dihydronaphthothiophenes were obtained.At higher temperatures 2-arylnaphthothiophenes and 2,3-dihydronaphthothiophene were isolated.Attempts are made to rationalize the formation of these products in terms of protonation of naphthothiophene by moist aluminum chloride and reaction of the resulting electrophile with an aromatic substrate.
- Clark, Peter David,McKinnon, David M.
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p. 1297 - 1302
(2007/10/02)
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