Experimental and Theoretical Investigations into the Unusual Regioselectivity of 4,5-, 5,6-, and 6,7-Indole Aryne Cycloadditions

The 6,7-indolyne shows remarkable regioselectivity in its cycloaddition with 2-substituted furans. Electron-donating groups give predominantly the more sterically crowded product, while electron-withdrawing groups display the opposite regioselectivity. By contrast, 4,5- and 5,6-indolynes show no reg...

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Bibliographic Details
Published in:Organic letters 2010-01, Vol.12 (1), p.96-99
Main Authors: Garr, Ashley N, Luo, Diheng, Brown, Neil, Cramer, Christopher J, Buszek, Keith R, VanderVelde, David
Format: Article
Language:English
Subjects:
Cyclization
Indoles - chemistry
Models, Theoretical
Molecular Structure
Stereoisomerism
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Summary:The 6,7-indolyne shows remarkable regioselectivity in its cycloaddition with 2-substituted furans. Electron-donating groups give predominantly the more sterically crowded product, while electron-withdrawing groups display the opposite regioselectivity. By contrast, 4,5- and 5,6-indolynes show no regioselectivity. Optimized electronic structure calculations using the M06-2X density functional and 6-311+G(2df,p) basis set revealed that the 6,7-indolynes are highly polar structures and that their cycloadditions have substantial electrophilic substitution character that leads to the observed preference for contrasteric products.
ISSN:1523-7060
1523-7052
DOI:10.1021/ol902415s