New Efficient Synthesis of 1,4-Benzodiazepin-5-ones by Catalytic Aza-Wittig Reaction

Abstract

1,4-Benzodiazepin-5-ones were synthesized in 71–89% yields from 2-isocyanato-<i>N</i>-(2-oxoalkyl)benzamides via a new catalytic intramolecular aza-Wittig reaction. Starting from easily accessible phthalic anhydride and α-arylamino ketones, the corresponding 2-{[(2-oxoalkyl)amino]carbonyl}benzoic acids underwent sequential formation of the acid azide and Curtis rearrangement to give 2-isocyanato-<i>N</i>-(2-oxoalkyl)benzamides that were reacted directly to give the final 2,4-diaryl-3,4-dihydro-5<i>H</i>-1,4-benzodiazepin-5-ones and 4-aryl-2-<i>tert</i>-butyl-3,4-dihydro-5<i>H</i>-1,4-benzodiazepin-5-ones.