Direct transition-metal-free synthesis of 2-heteroaryl-4-quinolones via ANRORC type rearrangement of 3-(2-(2-nitrophenyl)-2-oxoethyl)quinoxalin-2(1H)-ones

Abstract

A novel, metal-free, reductive intramolecular ANRORC-type rearrangement of nitrobenzenes and unmodified imines has been developed, providing simple and direct access to a wide range of 2-(benzimidazol-2-yl)quinolin-4(1H)-ones via a transformation sequence involving N(sp³)–H functionalization/N(sp³)–C(sp²) bond formation via nucleophilic addition/ring opening with N(sp³)–C(sp³) bond cleavage/ring closure with C(sp²)–C(sp²) bond formation from readily accessible 3-(2-(2-nitrophenyl)-2-oxoethyl)quinoxalin-2(1H)-ones, using sodium dithionite as a reducing agent. The utility of this methodology is further demonstrated in the synthesis of 2-(imidazo[4,5-b]pyridin-2-yl)quinolin-4(1H)-one, 2-(purin-8-yl)quinolin-4(1H)-one and 2-(imidazole-2-yl)quinolin-4(1H)-one hybrids as well as the 2,2′-([5,5′-bibenzimidazole]-2,2′-diyl)bis(quinolin-4(1H)-one) scaffold.