AbstractMethylation ofN‐substituted 1,2‐thiazetidine 1,1‐dioxides in the presence of lithium diisopropylamide (LDA) yields 4,4‐dimethyl derivatives. Monomethylation only occurs when one position at C‐4 is blocked by a silyl group, which, afterwards, can be removed by treatment with tetrabutylammonium fluoride (TBAF). A silyl protecting group at the nitrogen is easily removed by cleavage with TBAF on silica gel under mild c