Densely functionalized 2-methylideneazetidines from nitrodienic building blocks

Novel, densely functionalized 2-methylideneazetidines can be obtained in high yields under mild conditions from the reactions of nitropentadienoates with primary amines, most likely through an aza-Michael addition followed by a 4-exo-trig cyclization. The initial, selective trans arrangement of the C3 and C4 ring hydrogens undergoes stereomutation due to the presence of an easily enolizable site at C3, eventually leading to mixtures in which the cis isomer generally prevails.