A 1,3-dipolar cycloaddition reaction of nonstabilized azomethine ylides and cyclic N-sulfonyl imines has been developed providing a workable access to imidazolidine-fused sulfamidates, sulfamides, and benzosultams bearing a quaternary center. Distinct from the available literature, this current work enables to make entry, for the first time, into the novel imidazolidine-fused sulfamidates and sulfamides. Furthermore, the selective imidazolidine ring opening accompanied by CH2 extrusion yielded tetra-substituted sulfamidates with an aminomethyl group. In addition, imidazolidine ring opening coupled with SO2 extrusion provided synthetically useful 1,2-diamines.