Downey CW, Poff CD, Nizinski AN. Friedel-Crafts Hydroxyalkylation of Indoles Mediated by Trimethylsilyl Trifluoromethanesulfonate.
J Org Chem 2015;
80:10364-9. [PMID:
26393376 DOI:
10.1021/acs.joc.5b01681]
[Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Indoles and N-alkylindoles undergo Friedel-Crafts addition to aldehydes in the presence of trimethylsilyl trifluoromethanesulfonate and a trialkylamine to produce 3-(1-silyloxyalkyl)indoles. Neutralization of the reaction mixture with pyridine followed by deprotection under basic conditions with tetrabutylammonium fluoride provides the 1:1 adduct as the free alcohol. This method prevents spontaneous conversion of the desired products to the thermodynamically favored bisindolyl(aryl)methanes, a process typically observed when indoles are reacted with aldehydes under acidic conditions.
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