Ring expansion of nitrogen-containing chloromethylheteroalicycles via aziridinium intermediates

Abstract

The nucleophilic reaction of NaN3 with the chloromethylheteroalicycles, 4-benzyl-3chloromethyl-morpholine 5a, -tetrahydro-4H-1,4-thiazine 5b, -1-methylpiperazine 5c and 1-benzyl-2-chloromethylpiperidine 5d, gave the ring-expanded compounds 6-azido-4-benzylhexahydro-1,4-oxazepine 11a and its analogues 11b–d along with the normally substituted compounds 3-azidomethyl-4-benzylmorpholine 10a and its analogues 10b–d in varying ratios. LUMO frontier electron densities of the reaction centres indicated that the reaction proceeded via the aziridinium intermediate 9 and accounted for the predominance of the reaction product 10 or 11.