New methodology for the preparation of pyrrole and indole derivatives via iminophosphoranes:synthesis of pyrrolo[1,2-a]quinoxalines, indolo[3,2-c]quinolines and indolo[1,2-c]quinazolines

Abstract

The aza-Wittig reaction of iminophosphorane N-[o-(triphenylphosphoranylidene)amino]-phenyl pyrrole 4 with heterocumulenes leads to functionalized pyrrolo[l,2-a]quinoxalines. Iminophosphorane 19 , derived from 2-(o-amino)phenyl indole, reacts under mild conditions with isocyanates to form 21 which are converted into 5-amino-11H-indolo[3,2-c]quinolines 22 . Iminophosphorane 19 also reacts with carbon dioxide and carbon disulfide to give indolo[3,2-c]quinolines 23 . Iminophosphorane 28 . derived from 2-fo-azido)-phenyl-3-phenyl indole, reacts with isocyanates, carbon dioxide and carbon disulfide to form indolo[l,2-c]-quinazolines 29 and 30 respectively.