Adventures in CH-Arylation Chemistry

Abstract

The present article provides a personalized account on CH-arylation reactions employed for the synthesis of heterocycles. The presence of a nitro group allowed for direct and regioselective CH-arylations of pyrazoles, imidazoles, indoles and a variety of purine analogues. Direct CH-arylations without the presence of an activating nitro-group were employed for inter- and intramolecular reactions of purine derivatives, which allowed for the synthesis of a great variety of polycyclic systems. Domino C–N coupling / hydroamination / CH-activation reactions of diarylacetylenes with anilines allowed for the synthesis of polycondensated N-heterocycles. Products include indolo- and azaindolo[1,2-f]phenanthridines, quinolino[3′,4′:4,5]pyrrolo[1,2-f]phenanthridines, pyrimido[5′,4′:4,5]pyrrolo[1,2-f]phenanthridines, and benzothieno[2′,3′:4,5]pyrrolo[1,2-f]phenanthridines. The reaction of N-heterocycles, such as indoles, with 1,1-difluoroalkenes resulted in a twofold addition-elimination reaction to give 1,1-diaminoalkenes, which were transformed by CH-arylation into various polycondensated heterocycles, such as indoloisoquinolines, thienoindolizines, oxepines and helicenes. Pyridofluoranthenes, diindenopyrene and azadiindenopyrenes were prepared by a combination of Pd-catalyzed cross-coupling reactions with acid-mediated cycloisomerizations and Pd-catalyzed intramolecular CH-arylations. Bis(carbazoles), benzodithiazoles, benzodithiophenes and 2,5-diarylpyrroles were prepared by inter- and intramolecular CH-arylation reactions.