The reactivity of N-tosylphenylaziridine versus N-tosylphenylazetidine in heterocyclization reactions

N-Tosylaziridine (1) and N-tosylazetidine (2) react as 1,3 and 1,4 masked dipoles with electron rich alkenes, respectively, either under kinetic or thermodynamic control. The reactivity of the new aza oxo [4.4.0] 9, a precursor of N-tosyliminium, was exploited for the preparation of stereodefined substituted piperidines.