A new diastereo- and enantioselective copper-catalyzed conversion of alkynyl epoxides into α-allenic alcohols

Chiral copper complexes of BINOL- and TADDOL derived phosphorus amidites proved to be highly effective catalysts for the alkylation of alkynyl epoxides with dialkylzinc reagents. The corresponding α-allenol reaction products (S N2′-pathway) were obtained with good to excellent regio- and diastereoselectivity. The e.e. values obtained for this reaction were in the range of 26–38 %. A number of different Cu(II)-complexes were screened as possible catalysts and the results obtained indicate a complete control of the diastereoselectivity with an easy access to both enantioenriched synand anti-α-allenols.