- Enantioselective Copper-Catalyzed Radical Ring-Opening Cyanation of Cyclopropanols and Cyclopropanone Acetals
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A novel approach for enantioselective cyanation of cyclopropanols and their derivatives through copper-catalyzed radical relay processes has been developed. Various cyclopropanols and cyclopropanone acetals are compatible to the catalytic conditions, providing β-carbonyl nitriles with excellent enantioselectivity. These products can be readily converted to chiral γ-amino acids derivatives and drugs such as (R)-baclofen. Preliminary mechanistic studies have supported a ring-opening process for cyclopropanoxy radicals followed by copper-catalyzed enantioselective cyanation of benzylic radicals to form the C?CN bonds in an enantioselective manner. (Figure presented.).
- Chen, Pinghong,Guo, Yin-Long,Liu, Guosheng,Wang, Lei,Wu, Lianqian
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supporting information
p. 2189 - 2194
(2020/04/17)
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- Difluorohomologation of ketones
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A method for the homologation of ketones with the CF2 fragment is described. The reaction involves silylation, room-temperature difluorocyclopropanation of silyl enol ethers, and selective ring opening of cyclopropanes under acidic conditions. The whole three-step sequence is conveniently performed in a one-pot mode.
- Kosobokov, Mikhail D.,Levin, Vitalij V.,Struchkova, Marina I.,Dilman, Alexander D.
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supporting information
p. 760 - 763
(2015/03/05)
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- Mechanistic studies on α-trifluoromethylation of ketones via silyl enol ethers and its application to other carbonyl compounds
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(Chemical Equation Presented) Synthesis of α-CF3 carbonyl compounds has been recognized to be difficult up to now because the polarization of CF3δ--Iδ+ is opposite to that of CH3δ+-Iδ-, and this makes it difficult to introduce CF3+ unit to enolates. We recently reported an effective R-trifluoromethylation of ketones by using Et 2Zn with Rh catalyst, but the mechanism has not fully been cleared. Now, we carried out the detailed mechanistic studies and found the involvement of a highly reactive alkylrhodium complex which derived from Et2Zn and RhCl(PPh3)3 in this α-trifluoromethylation. Furthermore, this α-trifluoromethylation was applied to other types of carbonyl compounds in good yields.
- Sato, Kazuyuki,Yuki, Takashi,Yamaguchi, Ryoji,Hamano, Tetsuya,Tarui, Atsushi,Omote, Masaaki,Kumadaki, Itsumaro,Ando, Akira
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supporting information; experimental part
p. 3815 - 3819
(2009/10/01)
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- Oxidation of Alkyl Trimethylsilyl Ketene Acetals with Lead(IV)
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Alkyl trimethylsilyl ketene acetals generated from either esters or lactones react with lead(IV) acetate (LTA) or lead(IV) benzoate (LTB) to afford useful yields of the corresponding α-carboyloxy esters and α-carboyloxy lactones.Yields of the reaction products are optimized by use of the appropriate solvent (methylene chloride or benzene) during oxidation.Alkyl groups such as methyl, ethyl, and tert-butyl are all compatible with the procedure, and lactones containing five-, six-, and seven-membered rings give good yields of oxidation products.
- Rubottom, George M.,Gruber, John M.,Marrero, Roberto,Juve, Henrik D.,Kim, Wan Chong
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p. 4940 - 4944
(2007/10/02)
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- Reactions of Trialkylsilyl Trifluoromethanesulfonates, II. - Synthesis of O-Alkyl-O-(trialkylsilyl)ketene Acetals and 2-(Trialkylsilyl)carboxylates
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Alkyl carboxylates 2 are silylated by trialkylsilyl triflates 1 in the presence of triethylamine (3) to yield ketene acetals 4.In reactions of the esters 6 mixtures of ketene acetals 7 and at the α-carbon silylated esters 8 are obtained.Ethanoic acid esters and lactones are doubly silylated to give the products 11, 12, and 15, respectively.Under suitable conditions silylation of the esters 10 gives rise to the 2-trimethylsilylethanoic acid esters 13.The thermodynamically more stable products are obtained.Product distributions depend on the structure of the esters and the silylating agents 1.
- Emde, Herbert,Simchen, Gerhard
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p. 816 - 834
(2007/10/02)
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- Synthesis of α-fluorocarbonyl compounds
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Process for preparing an organic compound of the formula R2 R2 CFC(O)R3, which process comprises contacting and reacting in a reaction mixture which includes an inert solvent, at a temperature of -40° C. to -100° C., ROF and STR1 R is polyfluoroperhaloalkyl of 1-6 carbon atoms or FOCF2 ; R1 is hydrocarbyl of 1-6 carbon atoms; each R2 is selected from H, alkyl of 1-17 carbon atoms, cycloalkyl of 3-6 carbon atoms, aryl, heteroaryl and such alkyl, cycloalkyl, aryl and heteroaryl substituted by halogen or alkoxy of 1-6 carbon atoms; R3 is selected from H, alkyl and haloalkyl of 1-16 carbon atoms, cycloalkyl of 3-10 carbon atoms, aryl and haloaryl, OSi(R1)3, OH, NH2, alkoxy of 1-6 carbon atoms, aryloxy, NHR1 and NR12 wherein R1 is alkyl of 1-6 carbon atoms, N-arylamino and nitrogen or sulfur heterocyclic of 4-5 carbon atoms; R3 and one R2 taken together is a diradical which with the C=C group is carbocyclic, heterocyclic or haloheterocyclic, and recovering from the reaction mixture the compound of the formula R2 R2 CFC(O)R3.
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