(E)-α-Sulfonamidocrotylboronates as Reagents for the Stereoselective Homoaldol Synthesis

The α-sulfonamidocrotylboronates 9 and 10 have been generated by nucleophilic substitution at the α-chlorocrotylboronates 1b, in yields of up to 70%. The α-sulfonamidocrotylboronates 9 and 10 react with aldehydes at room temp. and 4 kbar pressure to give the anti-homoallylic alcohols 13 and 14 with high simple diastereoselectivity. These latter may be directly converted into the lactol ethers 15 in a one-pot procedure.