[1,2-Benzenediolato(2−)-O-O′]oxotitanium. A Chemoselective and Efficient Catalyst for Aldol-type Reaction of Ketene Silyl Acetals with Aldehydes

In the presence of a catalytic amount of [1,2-benzenediolato(2−)-O,O′]oxotitanium, ketene silyl acetals smoothly react with aldehydes to afford the corresponding β-hydroxy carboxylic esters in good yields under mild conditions. According to this procedure, an aldehyde group is selectively activated, while an acid labile acetal group remains intact.