AXIALLY CHIRAL ALLENYLBORANES - CATALYTIC ASYMMETRIC-SYNTHESIS BY PALLADIUM-CATALYZED HYDROBORATION OF BUT-1-EN-3-YNES AND THEIR REACTION WITH AN ALDEHYDE

Reaction of but-1-en-3-ynes(CH2=CR-C=CH: R=H, n-C5H11) with catecholborane in the presence of a palladium catalyst bearing a chiral monodentate phosphine ligand, (S)-(-)-MeO-MOP, give optically active (3-substituted-1,2-butadienyl)-1,3,2-benzodioxaborolanes [Me(R)C=C=CH(BO2C6H4)], the reaction of which with benzaldehyde proceeded with syn attack to give the corresponding optically active but-3-ynyl alcohols of up to 61% enantiomeric excess (e.e.).