Highly Enantioselective Sequential Hydrogenation of Ethyl 2-Oxo-4-arylbut-3-enoate to Ethyl 2-Hydroxy-4-arylbutyrate
摘要:
The hydrogenation of (E)-ethyl 2-oxo-4-arylbut-3-enoate with [NH2Me2](+)[{RuCl [(S)-SunPhos]}2(mu-Cl-3] gave ethyl 2-hydroxy-4-arylbutyrate with 94-96% ee. Further investigation has proved that the hydrogenation proceeded via a sequential hydrogenation of C = O and C = C bonds, which is sensitive to the reaction temperature. Hydrolysis of ethyl 2-hydroxy-4-phenylbutyrate (ee 93%) provided the 2-hydroxy-4-phenylbutyric acid with 81 % yield at 99% ee after a single recrystallization from 1, 2-dichloroethylene.
Synthesis of 5-unsubstituted dihydropyrimidinone-4-carboxylates from deep eutectic mixtures
作者:Sangram Gore、Sundarababu Baskaran、Burkhard König
DOI:10.3762/bjoc.18.37
日期:——
A facile one-pot synthesis of 5-unsubstituted dihydropyrimidinones from β,γ-unsaturated ketoesters in low melting ʟ-(+)-tartaric acid–N,N-dimethylurea mixtures is reported. This solvent-free method is very general and provides easy access to 5-unsubstituted dihydropyrimidinone-4-carboxylate derivatives in good yields.
DABCO-catalyzed regioselective cyclization reactions of β,γ-unsaturated α-ketophosphonates or β,γ-unsaturated α-ketoesters with allenic esters
作者:Cheng-Kui Pei、Lei Wu、Zhong Lian、Min Shi
DOI:10.1039/c1ob06507f
日期:——
Highly efficient DABCO-catalyzed [4 + 2] cycloaddition of β,γ-unsaturatedα-ketophosphonates or β,γ-unsaturated α-ketoesters with allenicesters gives the corresponding highlyfunctionalized tetrahydropyran and dihydropyran derivatives in good to excellent yields and moderate to good regioselectivities under mild conditions.
Deracemisation of aryl substituted α-hydroxy esters using Candida parapsilosis ATCC 7330: effect of substrate structure and mechanism
作者:B. Baskar、N.G. Pandian、K. Priya、Anju Chadha
DOI:10.1016/j.tet.2005.09.104
日期:2005.12
Candida parapsilosis ATCC 7330 was found to be an efficient biocatalyst for the deracemisation of aryl alpha-hydroxy esters (65-85% yield and 90-99% ee). A variety of aryl and aryl substituted alpha-hydroxy esters were synthesized to reflect steric and electronic effects on biocatalytic deracemisation. The mechanism of this biocatalytic deracemisation was found to be stereoinversion. (c) 2005 Elsevier Ltd. All rights reserved.