Addition of RC(O)CI (R = Oft, Me, or Ph) across the highly strained N-C(3)
sigma-bond in 3-bromomethyl-1-azabicyclo[1.1.0]butane (1) afforded the corr
esponding N-acyl-3-bromomethyl-3-chloroazetidines (2a-2c, respectively). Su
bsequent zinc promoted eliminative dehalogenation of 2a-2c produced the cor
responding N-acyl-3-methyleneazetidines (3a-3c, respectively). Finally, ozo
nolysis of 3a-3c afforded the corresopnding N-acylazetidin-3-ones (4a-4c, r
espectively).