Functionalization of four-membered cyclic sulfoximines by a convenient lithiation/trapping sequence

The functionalization of four-membered cyclic sulfoximine, based on a lithiation/electrophile trapping sequence, led to unprecedented C(2)-substituted N-Boc-1-imino-16-thietane 1-oxide in moderate to good yields. Interestingly, the reaction proceeded with high stereocontrol showing a preferential bias for an introduction of the electrophile syn to the oxygen on the sulfur. Starting from thietan- 1-one, by a combination of lithiation/electrophile trapping followed by N-transfer, it is possible to obtain the stereoisomer bearing the electrophile syn to the nitrogen on the sulfur. Thus, all stereoisomers can be accessible for medicinal chemistry studies.