Synthesis of spiro[pyrrole-2,5′-[1,3]thiazoles] by heterocyclization of pyrrolobenzoxazinetriones with thiobenzamide

Heterocyclizations of hetareno[e]pyrrole-2,3-diones (1H-pyrrole-2,3-diones fused through the N–C bond to nitrogen heterocycles) by the action of binucleophiles provide convenient methods for the synthesis of various five-, six-, and seven-membered nitrogen heterocycles, as well as fused, bridged, and spiro heterocyclic systems [1–5]. We previously showed that reactions of 3-acylpyrrolo[2,1-c][1,4]benzoxazine-1,2,4triones (1H-pyrrole-2,3-diones fused through the N–C bond to 1,4-benzoxazin-2-one) with C,O[5, 6], C,N[5, 7–9], and N,N-1,3-binucleophiles [5, 10] give rise to spiro[furan-3,2′-pyrrole], 2,3′-spirobipyrrole, and spiro[imidazole-4,2′-pyrrole] derivatives. Reactions of pyrrolobenzoxazinetriones with N,S-1,3-binucleophiles were not studied previously.