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 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.
Garr
Ashley N
AN
Department of Chemistry and Supercomputing Institute, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, USA.
Luo
Diheng
D
Brown
Neil
N
Cramer
Christopher J
CJ
Buszek
Keith R
KR
VanderVelde
David
D
D003500:Cyclization; D007211:Indoles / Q000737:chemistry*; D008962:Models, Theoretical; D015394:Molecular Structure; D013237:Stereoisomerism
D007211:Indoles