Tertiary amine catalyzed ring expansion reaction of N-tosylaziridines to 2-aroyl-N-tosylazetidines, with nitrogen ylides formed in situ from phenacyl bromide derivatives in a silica gel-water system is reported. The reaction expeditiously affords functionalized azetidines in high yields and stereoselectivities in a one-pot process. Advantageously, the protocol precludes the preparation and isolation of nitrogen ylides and their precursors in a separate step as they are formed in situ.
