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).