Three-component reaction of 3-(diethoxyphosphoryl)coumarin, enolizable ketones and primary amines: Simple, stereoselective synthesis of benzo[1,3]oxazocine skeletons

Abstract

The synthesis of benzoxazocine phosphonates was accomplished by means of the three-component reaction of 3-(diethoxyphosphoryl)coumarin, enolizable ketones and benzylamine. An asymmetric version of this reaction was also developed. Treatment of the coumarin with cyclopentanone and (R)- or (S)-1-phenylethylamine afforded enantiomerically pure benzoxazocine phosphonates in a 2.5 : 1 diastereoisomeric ratio. In contrast, similar reaction with cyclohexanone provided α-phosphono-δ-enamides as single diastereoisomers. The mechanistic features of the reaction were discussed. A transition state model rationalizing its stereochemical outcome was proposed. The α-phosphono-δ-lactams obtained were transformed into the corresponding α-methylene-δ-lactams. The cytotoxicity of these compounds was evaluated.