Diastereoselectivity which is induced by the use of 2-imidazolidinone auxil
iaries is greatly dependent on the N-substituents of the heterocycles, amon
g which the bulky arenesulfonyl group is the moiety of choice. Reactions of
this type afford an excellent level of diastereoselection in the methylati
on of N'-butyryl-2-imidazolidinones via the metal enolates. (C) 2000 Publis
hed by Elsevier Science Ltd.