Formation of 4,5,6,7-tetrahydroisoindoles by palladium-catalyzed hydride reduction

Duen Ren Hou, Ming Shiang Wang, Ming Wen Chung, Yih Dar Hsieh, Hui Hsu Gavin Tsai

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22 Scopus citations

Abstract

(Chemical Equation Presented) Substituted 1,3-dihydro-2H-isoindoles (2, isoindolines) were prepared and subjected to palladium-catalyzed formate reduction. Alkyl isoindolines were reduced to 4,5,6,7-tetrahydro-2H-isoindoles (1). Only partial reduction was observed for 5-methoxyisoindoline, and 4-methoxy-, 5-carbomethoxy-, amino-, and amidoisoindolines were inert to the reaction. Halogen-substituted isoindolines were dehalogenated and reduced to 4,5,6,7-tetrahydro-2H-isoindoles. Isoindole 24 was also reduced to a mixture of an isoindoline and a 4,5,6,7-tetrahydro-2H-isoindole. In contrast, 2,3-dihydro-1H-indoles 21 underwent dehydrogenation to give thermodynamically stable indoles. Theoretical calculations show the significant difference in aromaticity between isoindoles and indoles, corresponding to the observed differences in reactivities. Tetrahydro-2H-isoindoles 1 were oxidized to 4,5,6,7-tetrahydroisoindole-1,3-diones in the presence of NBS and air.

Original languageEnglish
Pages (from-to)9231-9239
Number of pages9
JournalJournal of Organic Chemistry
Volume72
Issue number24
DOIs
StatePublished - 23 Nov 2007

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