SummaryThe synthesis of 5-substituted 6,6a-dihydroisoindolo[2,1-a]quinolin-11(5H)-ones via [4 + 2] imino-Diels–Alder cyclization from N-aryl-3-hydroxyisoindolinones and N-vinyl lactams under Lewis acid-catalysed anhydrous conditions is reported. Reactions of N-(2-substituted-aryl)-3-hydroxyisoindolinones with N-vinylpyrrolidone under identical conditions resulted in the formation of 2-(2-substitued-aryl)-3-(2-(2-oxopyrrolidin-1-yl)vinyl)isoindolin-1-one analogues indicating steric hinderance as the cause of deviation. The probable mechanism of the reaction based on the results from X-ray crystallography and molecular modelling is discussed.

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Further synthetic utility of 3-substituted N-arylisoindolinones obtained from N-aryl-3-hydroxyisoindolinones and alkyl aryl ketones under Lewis acid mediated anhydrous conditions is reported. Herein, substituted 6,6a-dihydroisoindolo[2,1-a]quinolin-11(5H)-ones were synthesized from 3-substituted isoindolinones following a NaBH 4 ketone reduction and carbocation-mediated intramolecular electrophilic aromatic substitution using BF 3 •OEt 2. Representative final products were unambiguously characterized by single-crystal X-ray crystallography.

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