Catalytic asymmetric synthesis of <i>Secondary</i> (<i>E</i>)‐allyl alcohols from acetylenes and aldehydes <i>via</i> (1‐alkenyl)zinc intermediates. Preliminary Communication

Abstract

Abstract Hydroboration of aliphatic 1‐alkynes with freshly prepared dicyclohexylborane (1 mol‐equiv., hexane), treatment of the resulting [( E )‐1‐alkenyl]boranes 5 with Et 2 Zn or Me 2 Zn (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. NH 4 Cl provided ( E )‐allyl alcohols 6 usually in 70–95% yield with 79–98% enantiomeric excess ( Scheme 3 and Table ).