Enantioselective Organocatalytic Reduction of β-Trifluoromethyl Nitroalkenes: An Efficient Strategy for the Synthesis of Chiral β-Trifluoromethyl Amines
β‐trifluoromethyl‐substituted nitroalkenes, mediated by 3,5‐dicarboxylic ester‐dihydropyridines (Hantzsch ester type), has been successfully developed. A multifunctional thiourea‐based (S)‐valine derivative was found to be the catalyst of choice, promoting the reaction in up to 97 % ee. The methodology has been applied to a wide variety of substrates, leading to the formation of differently substituted precursors
Organocatalytic Asymmetric Transfer Hydrogenation of Nitroolefins
作者:Nolwenn J. A. Martin、Lidia Ozores、Benjamin List
DOI:10.1021/ja074045c
日期:2007.7.1
We describe a highly efficient and highly enantioselective Hantzsch ester mediated conjugate transfer hydrogenation of beta,beta-disubstituted nitroolefins that is catalyzed by a Jacobsen-type thiourea catalyst.
(Thio)urea Organocatalyst Equilibrium Acidities in DMSO
作者:Gergely Jakab、Carlo Tancon、Zhiguo Zhang、Katharina M. Lippert、Peter R. Schreiner
DOI:10.1021/ol300307c
日期:2012.4.6
Bordwell's method of overlapping indicators was used to determine the pK(a) values of some of the most popular (thio)urea organocatalysts via UV spectrophotometric titrations. The incremental effect of CF3 groups on acidic strength was also investigated. The pic's are in the range of 8.5-19.6. The results may lead to a better understanding of noncovalent organocatalysis and may aid in future catalyst development.