Synthesis of nitidine (8,9-dimethoxy-5-methyl-2,3-methylenedioxybenzo[c]phenanthridinium); a comparison of electrochemical and photochemical methods

Abstract

Electrochemical reduction of the 2-bromo-N-methyl-N-naphthylbenzamide (5) gave a 1-phenylnaphthalene derivative and no benzophenanthridone. The latter was the sole product from photocyclisation of the amide (5). The electrochemical reaction generates an aryl radical which attacks the adjacent naphthalene ring to give the product isolated, whereas the photoreaction probably proceeds by cyclisation of the excited state of (5) to form a new six-membered ring and then loss of hydrogen bromide. The benzophenanthridone was converted into nitidine tetra-fluoroborate.