ENANTIOPOSITION-SELECTIVE ALKYNYLATION OF BIARYL DITRIFLATES BY PALLADIUM-CATALYZED ASYMMETRIC CROSS-COUPLING

Asymmetric cross-coupling of prochiral biaryl ditriflate, [[(trifluoro methyl)sulfonyl]oxy]phenyl]naphthalene (1) or luoromethyl)sulfonyl]oxy ]-2-(biphenyl-2-yl)benzene (4) with triphenylsilylethynylmagnesium bro mide in the presence of lithium bromide and 5 mol % of palladium catal yst, PdCl2[(S)-Alaphos], proceeded with high enantioposition selectivi ty to give high yields of the corresponding axially chiral monoalkynyl ated biaryls, 2a or 2d, of high enantiomeric purity (up to >99% ee). C opyright (C) 1996 Elsevier Science Ltd