Thermolyzed products of naphth[1,2-d]imidazo[2,1-b]-thiazole-2,3-dione

Themolysis of naphth[1,2-d]imidazo[2,1-b]thiazole-2,3-dione (1) in dimethylformamide gave an intermediate 2-isocyanatonaphtho[1,2-d]thiazole (2), which underwent [4 + 4] cyclodimerization to yield dinaphtho-[1″,2″:4,5;1′″,2′″:4′,5′]dithiazolo[3,2-a:3′,2′-e]-1,3,5,7-tetrazocine-9,19-dione (3). The possible [4 + 2] cycloadduct, 3-(2-naphtho-[1,2-d]-thiazolyl)naphtho[1′,2′:4,5]thiazolo[3,2-a]-1,3,5-triazine-2,4-dione (4), an usual dimer type of heterocyclic isocyanates was not produced. Discrimination between the two isomers was established on the basis of spectral analyses.