Highly enantioselective alkynylation of alpha-keto ester: an efficient method for constructing a chiral tertiary carbon center.
The asymmetric addition of terminal alkynes to alpha-keto ester was carried out using a catalytic amount of (1S,2S)-3-(tert-butyldimethylsilyloxyl)-2-N,N-(dimethylamino)-1-(p-nitrophenyl)-propane-1-ol in the presence of Zn(OTf)(2) to give the corresponding tertiary propargylic alcohols in high yields with up to 94% ee. N-Methylephedrine and Zn(OSO(2)CHF(2))(2) were also examined in this reaction. [reaction: see text]