CATALYTIC ASYMMETRIC-SYNTHESIS OF SECONDARY (E)-ALLYL ALCOHOLS FROM ACETYLENES AND ALDEHYDES VIA (1-ALKENYL)ZINC INTERMEDIATES - PRELIMINARY COMMUNICATION

Hydroboration of aliphatic 1-alkynes with freshly prepared dicyclohexylborane (1 mol-equiv., hexane), treatment of the resulting [(E)-1-alkenyl]boranes 5 with Et2Zn or Me2Zn (1.05 mol-equiv.) followed by addition of (-)-3-exo-(dimethylamino)isoborneol (DAIB, 8; 0.01 mol-equiv.), subsequent addition of a solution of an aromatic or aliphatic aldehyde (1 mol-equiv., hexane). and quenching with aq. NH4Cl provided (E)-allyl alcohols 6 usually in 70-95% yield with 79-98% enantiomeric excess (Scheme 3 and Table).