Diphosphine-Catalyzed Mixed Double-Michael Reaction: A Unified Synthesis of Indolines, Dihydropyrrolopyridines, Benzimidazolines, Tetrahydroquinolines, Tetrahydroisoquinolines, Dihydrobenzo-1,4-oxazines, and Dihydrobenzo-3,1-oxazines

Seven different types of benzannulated N-heterocycles-indolines, dihydropyrrolopyridines, benzimidazolines, dihydrobenzo-3,1-oxazines, benzomorpholines, tetrahydroquinolines, and tetrahydroisoquinolines-can be obtained from simple dinucleophiles and electron-deficient acetylenes in one synthetic step. This powerful methodology was made possible through the use of diphenylphosphinopropane (DPPP) as the catalyst, with acetic acid and sodium acetate used as additives in some cases. The benzannulated N-heterocycles were isolated in excellent yields under mild metal-free conditions; they were purified without the need for aqueous workups.