Contrasting steric effects of the ketones and aldehydes in the reactions of the diisopinocampheyl enolborinates of methyl ketones with aldehydes
作者:P.Veeraraghavan Ramachandran、Wei-chu Xu、Herbert C. Brown
DOI:10.1016/0040-4039(96)00969-0
日期:1996.7
representative series of aldehydes, both of differing steric requirements provides aldols whose enantiomeric purities depend on the steric requirements of both the ketones and the aldehydes. This study has shown that increasing the steric requirements of the R group in the ketones has a pernicious effect on the ee, while increasing the steric requirements of the R group in the aldehydes exerts a beneficial
Chiral 1,3-oxazolidines are readily prepared from methyl ketones and chiral norephedrine. Formation of stannous azaenolates from the oxazolidines and reaction with aldehydes followed by removal of the chiral auxiliary lead to the aldol products in high level of enantiomeric purity.
A chiral hydrobenzoin/Ca complex catalyzes the reaction of acetophenone and aliphatic aldehydes to give the corresponding aldol products in up to 91% ee.
手性氢安息香/ Ca复合物催化苯乙酮与脂族醛的反应,得到相应的羟醛产物,其ee含量高达91%。
Dicationic ((−)-sparteine)palladium-catalyzed enantioselective aldol reaction of aldehydes with 1-phenyl-1-trimethylsilyloxyethene, proceeding via a palladium enolate
A dicationic ((−)-sparteine)palladium complex underwent a superior catalytic enantioselective aldol reaction of aldehydes with 1-phenyl-1-trimethylsilyloxyethene performing satisfactorily, starting with ((−)-sparteine)PdCl2 and AgSbF6 as catalyst precursors (1 mol % loading) in the presence of 3 Å molecular sieves over the reaction.
Direct catalytic asymmetric aldol reactions promoted by a novel barium complex
作者:Yoichi M.A. Yamada、Masakatsu Shibasaki
DOI:10.1016/s0040-4039(98)01120-4
日期:1998.7
A directcatalyticasymmetricaldolreaction of an aldehyde and an unmodifiedketone promoted by an asymmetric barium complex has been achieved. The possible structure of the barium catalyst, BaB-M, which possesses the function of a Lewis acid and a Brønsted base, was characterized by LDI-TOFMS, 13C-NMR spectroscopy and extensive studies of reaction conditions.