Enantioselective desymmetrizing palladium catalyzed carbonylation reactions: the catalytic asymmetric synthesis of quaternary carbon center containing 1,3-dienes
作者:Simon J. Byrne、Anthony J. Fletcher、Paul Hebeisen、Michael C. Willis
DOI:10.1039/b923186b
日期:——
A desymmetrization protocol has been used to develop a palladium catalyzed enantioselective carbonylation process. Achiral cyclic bis-alkenyltriflates are converted to their corresponding monoester derivatives with selectivities of up to 96% ee.
Comparative reductive desymmetrization of 2,2-disubstituted-cycloalkane-1,3-diones
作者:Jeremy M. Carr、Timothy S. Snowden
DOI:10.1016/j.tet.2008.01.065
日期:2008.3
Reductive desymmetrization of 2-methyl-2-substituted-cycloalkane-1,3-diones can be effected using either NaBH(4) in DME or lithium tri-tert-butoxyaluminum hydride (LTBA) in THF at -60 degrees C. The former is a new approach that offers slightly greater diastereoselectivity in the reduction of 2,2-disubstituted-cyclopentane- 1,3-diones while LTBA is superior with 2,2-disubstituted-cyclohexane- 1,3-diones. Both conditions minimize subsequent reduction to diols thereby furnishing high yields of 1,3-ketols. Particularly rapid monoreductions are observed with 2-methyl-2-nitroethylcyclopentane-1,3-dione and 2-cyanoethyl-2-methylcyclopentane-1,3-dione when treated with NaBH(4) in DME at -60 degrees C. As expected, diastereoselectivity varies considerably with the substitution at C-2. (C) 2008 Elsevier Ltd. All rights reserved.
Asymmetric microbial reduction of prochiral 2,2,-disubstituted cycloalkanediones
作者:Dee W. Brooks、Hormoz Mazdiyasni、Paul G. Grothaus
DOI:10.1021/jo00391a009
日期:1987.7
Chiral cyclohexanoid synthetic precursors via asymmetricmicrobial reduction of prochiral cyclohexanediones
作者:Dee W. Brooks、Hormoz Mazdiyasni、Sharmistha Chakrabarti
DOI:10.1016/s0040-4039(01)80123-4
日期:1984.1
Poly(ethylene Glycol) (400) as Superior Solvent Medium against Ionic Liquids for Catalytic Hydrogenations with PtO<sub>2</sub>
Adams' catalyst in poly(ethylene glycol) (PEG) (400) has been found to be a superior solvent over the ionic liquids by severalfold in promoting the hydrogenation of various functional groups. Both the catalyst and PEG were recycled efficiently over 10 runs without loss of activity, and substrate cross contamination was not observed despite a change in the substrate four times.