ON THE AZETIDIN-2-ONE RING FORMATION - A H-1-NMR INVESTIGATION

Azetidin-2-ones were prepared by addition of phenylacetic acid chloride to substituted benzal-anilines in DMF. The effect of temperature and substituents at the benzal-anilines on the reaction mechanism was investigated, carrying out the reaction in DMF d7 in an NMR probe of a Bruker 400-MHz spectrometer, at 25 and 60-degrees-C. Proton signals, arising from two kinds of intermediates, a 2-phenyl-N-(alpha-chlorobenzyl)-acetanilide (6) and a nitrogen-charged adduct (7), suggest that two competitive mechanisms play a role in the formation of trans and cis azetidin-2-ones.