Synthesis of Naphthoquinone Derivatives. XIII. Reaction of 2,3-Dihydro-2-thioxo-1H-naphth[2,3-d]imidazole-4,9-dione with Dimethyl Acetylenedicarboxylate

Abstract

Tetracyclic compounds with a thiazolidinone or thiazinone ring fused to 1H-naphth[2,3-d]imidazole-4,9-dione were synthesized. Dimethyl 2-(4,9-dioxo-4,9-dihydronaphth[2,3-d]imidazol-2-ylthio)fumarate (3) was obtained by a reaction of 2,3-dihydro-2-thioxo-1H-naphth[2,3-d]imidazole-4,9-dione with dimethyl acetylenedicarboxylate in methanol. A ring-closure reaction of 3 in acetic anhydride was found to give selectively methyl (3,5,10-trioxo-2,3,5,10-tetrahydronaphth[2′,3′ : 4,5]imidazo[2,1-b]thiazol-2-ylidene)acetate, while, the cyclization of 3 in polyphosphoric acid afforded methyl 4,6,11-trioxo-6,11-dihydro-4H-naphth[2′,3′ : 4,5]imidazo[2,1-b]thiazine-2-carboxylate.