Straightforward palladium-mediated synthesis of N-substituted 1,2-dihydrobenz[g]isoquinoline-5,10-diones

Related to our research on structural modifications of pentalongin, the active principle of the medicinal plant Pentas longiflora Oliv., a new synthesis of N-protected 1,2-dihydrobenz[g]isoquinoline-5,10-diones and their 4-methyl derivatives, which represent a new class of compounds, is reported. In both cases, the benz[g]isoquinoline skeleton was constructed by an intramolecular Heck reaction of N-protected 2-((allylamino)methyl)-3-bromo-1,4-dimethoxynaphthalenes and N-protected 2-((allylamino)methyl)-3-bromo-1,4-naphthoquinones, respectively.