A practical synthetic route to functionalized THBCs and oxygenated analogues via intramolecular Friedel-Crafts reactions

A practical catalytic approach to the synthesis of 4-substituted 1,2,3,4-tetrahydro-beta-carbolines (THBCs, 1) and 1,2,3,9-tetrahydropyrano[3,4-b]indoles (2) via InBr3-catalyzed intramolecular Friedel-Crafts (F-C) cyclization is described. The use of cross-metathesis reaction represents a direct rou...

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Bibliographic Details
Published in:Organic & biomolecular chemistry 2006-01, Vol.4 (17), p.3291-3296
Main Authors: Angeli, Marco, Bandini, Marco, Garelli, Andrea, Piccinelli, Fabio, Tommasi, Simona, Umani-Ronchi, Achille
Format: Article
Language:English
Subjects:
Carbolines - chemical synthesis
Carbolines - chemistry
Indicators and Reagents
Indoles - chemistry
Kinetics
Models, Molecular
Molecular Conformation
Oxidation-Reduction
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Summary:A practical catalytic approach to the synthesis of 4-substituted 1,2,3,4-tetrahydro-beta-carbolines (THBCs, 1) and 1,2,3,9-tetrahydropyrano[3,4-b]indoles (2) via InBr3-catalyzed intramolecular Friedel-Crafts (F-C) cyclization is described. The use of cross-metathesis reaction represents a direct route to the cyclization precursors and the use of InBr3 (5 mol%) allowed polycyclic indole compounds to be isolated in high yields under mild reaction conditions (rt, DCM, minutes). Finally, efforts toward the development of a stereocontrolled version of the present cyclization are presented, highlighting [salenAlCl] and bimetallic [(salenAlCl)2-InBr3] system as promising chiral Lewis acids (ee up to 60%).
ISSN:1477-0520
1477-0539
DOI:10.1039/b607864h