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

Abstract

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.