The Remarkable Effect of Titanium Tetraisopropoxide in Diastereoselective Reaction of Carbaldehydes with Chiral Benzenesulfonamide Lithium Complexes

Abstract

Chiral benzenesulfonamide titanium ate-complexes (4 and 8) were prepared from the lithium complexes (2 and 6) by treatment with titanium tetraisopropoxide. The diastereoselective reactions of aromatic carbaldehydes with 4 and 8 were performed, and the chiral o-(1-aryl-1-hydroxymethyl)benzenesulfonamides (3a-d and 7a-e) were obtained in 80-87% yields. The diastereomeric excesses (d.e.) of these products were evaluated as 62-82%. These compounds were also prepared from the lithium complexes (2 and 6), but the d.e. values were only 6-14% in this case.