Domino Reaction for Synthesis of Spiro[pyrazole‐4,5′‐pyrrolo[3,4‐c]carbazoles] and Spiro[pyrrolo[3,4‐c]carbazole‐5,5′‐thiazoles

Abstract

AbstractThe concentrated hydrochloride catalyzed reaction of 3‐(indol‐3‐yl)maleimides with (E)‐4‐arylidene‐5‐methyl‐2‐phenylpyrazol‐3‐ones in acetonitrile at room temperature afforded unexpected Michael addition product in high yields, which could be easily converted to the cis/trans‐diastereoisomers of spiro[pyrazole‐4,5′‐pyrrolo[3,4‐c]carbazoles] with the nearly 2 : 1 ratios by further oxidation with DDQ. On the other hand, the similar one‐pot two‐step reaction of 3‐(indol‐3‐yl)maleimides with (E)‐5‐arylidene‐2‐phenylthiazol‐4‐one predominately gave cis‐diastereoisomers of spiro[pyrrolo[3,4‐c]carbazole‐5,5′‐thiazoles] in satisfactory yields. The reaction mechanism included domino acid catalyzed Michael addition and DDQ oxidative coupling process