An efficient and enantioselective α-electrophilic difluoromethylation of β-keto esters has been achieved by phase-transfer catalysis. This procedure is applicable to different kinds of β-keto esters with a series of cinchona-derived C-2′ aryl-substituted phase-transfer catalysts. The reaction gives the corresponding products in good enantioselectivities (up to 83% ee) and yields (up to 92%) with high
An efficient and enantioselective photo-organocatalytic [small alpha]-hydroxylation of [small beta]- dicarbonyl compounds using molecular oxygen has been extended. This simple catalytic procedure is applicable to a range of [small beta]-keto esters and [small beta]-keto...
Inner Workings of a Cinchona Alkaloid Catalyzed Oxa-Michael Cyclization: Evidence for a Concerted Hydrogen-Bond-Network Mechanism
作者:Lukas Hintermann、Jens Ackerstaff、Florian Boeck
DOI:10.1002/chem.201203505
日期:2013.2.11
specificity. A concerted hydrogen‐bond network mechanism is proposed, in which the alkaloid hydroxy group acts as a general acid in the protonation of the α‐carbanionic center of the product enolate. The importance of concerted hydrogen‐bond network mechanisms in organocatalytic reactions is discussed. The relative stereochemistry of protonation is proposed as analytical tool for detecting concerted addition