Preparation of cinnolines and indoles from 2,β-dinitrostyrenes

Abstract

The reduction of 2,β-dinitrostyrenes (mainly with alkoxy- or benzyloxy-groups in the 4- and 5-positions) with various reagents is described. Catalytic hydrogenation yields indoles. Hydrazine in the presence of Raney nickel affords the azine and hydrazone of either the nitro- or amino-benzaldehyde from which the nitrostyrene was derived. Lithium aluminium hydride gives a mixture of indoles and cinnolines. Sodium borohydride yields 2,β-dinitrophenylethanes.