Enantioselective alkynylation of aldehydes catalyzed by a camphor sulfonylated amino alcohols titanium(IV) catalyst system

A new titanium(IV) complex has been developed for the effective enantioselective alkynylation of phenylacetylene addition to aldehydes. The titanium(IV) complex was readily prepared in situ from ( R )‐C‐(7,7‐dimethyl‐2‐oxo‐bicyclo[2.2.1]hept‐1‐yl)‐(1 R ,2 S )‐ N ‐(2‐hydroxy‐1,2‐diphenyl‐ethyl)‐methanesulfonamide (1h) and tetraisopropyl titanate [Ti( i ‐OPr) 4 ]. A variety of aromatic aldehydes and α,β‐unsaturated aldehydes were found to be suitable substrates in the presence of the camphor sulfonylated amino alcohol titanium(IV) complex [10 mol% 1h, 40 mol% Ti( i ‐OPr) 4 ]. The desired propargylic alcohols were afforded with high isolated yields (up to 90%) and moderate enantioselectivities (up to 65% ee) under mild conditions. Copyright © 2010 John Wiley & Sons, Ltd.