Convenient construction of spiro[indoline-3,5′-pyrrolo[3,4-c]carbazole] and spiro[indene-2,5′-pyrrolo[3,4-c]carbazole] via acid-catalyzed Diels-Alder reaction

p-TsOH catalyzed Diels-Alder reaction of 3-(indol-3-yl)maleimides with 3-phenacylideneoxindoles in toluene at 80 degrees C for two hours afforded cis/trans isomers of 3a',4',6',10c'-tetrahydrospiro[indoline-3,5'-pyrrolo[3,4-c]carbazoles] in nearly comparable yields, which could be easily converted to the corresponding 4',6'-dihydrospiro[indoline-3,5'-pyrrolo[3,4-c]carbazole] in high yields and with high diastereoselectivity by further DDQ oxidation. Additionally, the similar reaction of 3-(indol-3-yl) maleimides with 2-arylidene-1,3-indanediones in toluene 80 degrees C and sequential DDQ oxidation afforded functionalized dihydrospiro[indene-2,5'-pyrrolo[3,4-c]carbazoles] as major products. (c) 2020 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.

Automated summary

The p-TsOH catalyzed Diels-Alder reaction provides a method for the synthesis of various spiro compounds with different structures and properties from 3-(indol-3-yl)maleimides and different substrates.