New efficient synthesis of 2,3,4-trisubstituted 3,4-dihydroquinazolines by a Ugi 4CC/Staudinger/aza-Wittig sequence

Abstract

A series of 2,3,4-trisubstituted 3,4-dihydroquinazoline 3 was prepared by intramolecular aza-Wittig reaction of amide carbonyl groups with methyldiphenyl iminophosphorane, which was obtained from a Ugi 4CC/Staudinger sequence. Further intramolecular Heck reaction of 3d′– g′ in the presence of catalytic amount of Pd(OAc) 2 gave 6,12-dihydroindolo[2,1- b]quinazolines 4a– d in good yields.