Chelation-controlled additions to α-silyloxy aldehydes: an autocatalytic approach.

The Felkin-Anh model has been widely accepted to describe stereochemical outcomes in nucleophilic additions to α-silyloxy carbonyl compounds. Herein, it is demonstrated that chelation-controlled additions can be performed using dialkylzinc reagents in the presence of chlorotrimethylsilane with good to excellent diastereoselectivities. Ethyl zinc chloride, the Lewis acid responsible for promoting chelation, is generated in situ in an autocatalytic fashion. This approach circumvents its use in stoichiometric amounts.