Preparation of Thiolated Direct Aldol anti-Products

Significance

A very mild and operationally simple procedure was devised to obtain anti-aldol products 3 in high diastereoselectivity. The reaction obviates the usual need to work under an­hydrous conditions or at low temperatures. Noting that anti selectivity is less common in aldol chemistry, the authors conducted a thorough study of the reaction and showed that the stereo­chemical outcome of 3 is strongly dependent on the nature of the thiolate counterion. They propose that formation of an (E)-O-enolate is favored through coordination of a lithium ion to both sulfur atoms of the molecule.