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. 2010 Jan 1;12(1):96-9.
doi: 10.1021/ol902415s.

Experimental and theoretical investigations into the unusual regioselectivity of 4,5-, 5,6-, and 6,7-indole aryne cycloadditions

Ashley N Garr  1 , Diheng Luo, Neil Brown, Christopher J Cramer, Keith R Buszek, David VanderVelde
Affiliations

Experimental and theoretical investigations into the unusual regioselectivity of 4,5-, 5,6-, and 6,7-indole aryne cycloadditions

Ashley N Garr et al. Org Lett. .

Abstract

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.

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Figures

Figure 1
Figure 1
Benzenoid indole aryne (indolyne) systems.
Figure 2
Figure 2
Examples of complex indole natural products.
Scheme 1
Scheme 1
Regioselective 6,7-Indolyne Cycloadditions with 2-Substituted Furans
Scheme 2
Scheme 2
Furan and Azide Cycloadditions with 4,5-, and 5,6-Indolynes
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