Multicomponent access to novel dihydroimidazo[1′,5′:1,2]pyrido[3,4-b]indol-2-ium salts and indoles by means of Ugi/Bischler-Napieralski/heterocyclization two step strategy

A simple, efficient and general two step procedure, through a sequential Ugi reaction followed by a Bischler-Napieralski/heterocyclization tandem closure, to give novel 6,11-dihydro-5H-imidazo[1′,5′:1,2]pyrido[3,4-b]indol-2-ium salt derivatives, is described. By changing the amine and the acid components with ammonium formate, the same procedure affords 6,11-dihydro-5H-imidazo[1′,5′:1,2]pyrido[3,4-b]indole derivatives.