N-alkylindoles undergo Friedel–Crafts addition to aryl and secondary alkyl nitrones in the presence of trimethylsilyl trifluoromethanesulfonate and a trialkylamine to produce 3-(1- (silyloxyamino)alkyl)indoles. Spontaneous conversion to the bisindolyl(aryl)methanes, which is thermodynamically favored for nitrones derived from aromatic aldehydes, is suppressed under the reaction conditions. The silyloxyamino group can be deprotected with tetrabutylammonium fluoride to yield the hydroxylamine.
Copyright © 2021, Journal of Organic Chemistry.
Zachary Z. Oracheff, Helen L. Xia, Christopher D. Poff,* Scott E. Isaacson, C. Wade Downey. Friedel–Crafts addition of indoles to nitrones promoted by trimethylsilyl trifluoromethanesulfonate. Journal of Organic Chemistry 2021, 86, 17328-17336.