Studies on chromone derivatives. A direct and efficient one-pot synthesis of 4-chromone-linked 3-(N-acylamino)azetidin-2-ones from imines and N-acylalanine

Abstract

Chlorosulfonylmethylene(dimethyl)ammonium chloride 1 is found to be an efficient cyclodehydrating agent for the one-pot synthesis of various novel chromone-linked azetidin-2-ones 6via cyclo-addition reactions of 3-(aryliminomethyl)chromones 5 with in situ generated oxazolones 3, directly from the corresponding N-benzoylamino acids and there is no evidence for the formation of pyridones 7. The azetidinones 6a–g were obtained in 85–90% yields and their structures are fully corroborated by spectral and elemental analyses.