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

Themolysis of naphth1,2-d]imidazo2,1-b]thiazole-2,3-dione ( 1 ) in dimethylformamide gave an intermediate 2-isocyanatonaphtho1,2-d]thiazole ( 2 ), which underwent 4 + 4] cyclodimerization to yield dinaphtho-1″,2″:4,5;1′″,2′″:4′,5′]dithiazolo3,2-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)naphtho1′,2′:4,5]thiazolo3,2-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.