Condensation of 4-hydroxy-2-thiazolines with 1,2-phenylenediamine as a novel effective route to thiazolo[3,4-a]quinoxalines

Thiazolo[3,4-a]quinoxalin-4-ones were prepared in two steps starting from methyl phenylchloropyruvate using a new strategy for the construction of the ring system. A key step in this new method involves the reaction of 4-hydroxytetrahydrothiazoles with 1,2-phenylendiamines

Reaction for the Synthesis of Benzimidazol-2-ones, Imidazo[5,4‑<i>b</i>]‑, and Imidazo[4,5‑<i>c</i>]pyridin-2-ones via the Rearrangement of Quinoxalin-2-ones and Their Aza Analogues When Exposed to Enamines

A synthetically useful protocol has been developed for the preparation of highly functionalized <i>N</i>-pyrrolylbenzimidazol-2-ones. The reaction of variously substituted 3-aroyl- and 3-alkanoylquinoxalin-2­(1<i>H</i>)-ones with commercially available enamines in acetic acid results in a rapid rearrangement and formation of <i>N</i>-pyrrolylbenzimidazol-2-ones in modest to excellent yields. The key step of the rearrangement involves the novel ring contraction of 3-aroyl- and 3-alkanoylquinoxalin-2­(1<i>H</i>)-ones with enamines. In this case, the atom of carbon which is displaced from the pyrazine ring of quinoxalin-2­(1<i>H</i>)-one becomes the fourth carbon atom of the newly formed pyrrole ring. The method is applicable for the aza analogues of quinoxalin-2­(1<i>H</i>)-ones

Rearrangement of Quinoxalin-2-ones When Exposed to Enamines Generated in Situ from Ketones and Ammonium Acetate: Method for the Synthesis of 1‑(Pyrrolyl)benzimidazolones

The reaction of 3-benzoylquinoxalin-2­(1<i>H</i>)-ones with enamines (generated in situ from ammonium acetate and the corresponding methylaryl­(hetaryl)­ketones) proceeds smoothly to give the corresponding substituted 1-(pyrrolyl)­benzimidazolone derivatives in moderate yields through the novel rearrangement of 3-benzoylquinoxalin-2­(1<i>H</i>)-ones involving a dual cleavage of the C3N4 and C2-C3 bonds under mild conditions