[reaction: see text] Chloral or its hydrate undergoes the carbon-carbon bond-formation reaction with various optically active imines in the absence of any additive, followed by hydrolysis, to produce the corresponding beta-trichloromethyl-beta-hydroxy ketones in good yields with high enantioselectivities. In addition, the products with higher ee values were obtained by a simple recrystallization process
Practical asymmetric synthesis of β-hydroxy-β-trifluoromethylated ketones via the first example of the in situ generation of trifluoro-acetaldehyde and its successive asymmetric carbon–carbon bond formation reaction with chiral imines
Not only trifluoroactaldehyde ethyl hemiacetal or hydrate but also other polyfluoroalkylaldehydes acetals or hydrates react with an equimolar amount of various chiral imines, followed by hydrolysis to produce the corresponding (S)-beta-hydroxy-beta-polyfluoroalkyl ketones in good yields with good enantioselectivities; furthermore, the ee of the products can be improved by simple recrystallization.
Development of an Asymmetric Trimethylenemethane Cycloaddition Reaction: Application in the Enantioselective Synthesis of Highly Substituted Carbocycles
作者:Barry M. Trost、Steven M. Silverman、James P. Stambuli
DOI:10.1021/ja207550t
日期:2011.12.7
azetidine structures, is discussed. The conditions developed to effect an asymmetric TMM reaction using 2-trimethylsilylmethyl allyl acetate were shown to be tolerant of a wide variety of alkene acceptors, providing the desired methylenecyclopentanes with high levels of enantioselectivity. The donor scope was also explored, and substituted systems were tolerated, including one bearing a nitrile moiety. These