Bortolami M, Mattiello L, Scarano V, Vetica F, Feroci M.
In Situ Anodically Oxidized BMIm-BF
4: A Safe and Recyclable BF
3 Source.
J Org Chem 2021;
86:16151-16157. [PMID:
34213898 PMCID:
PMC8609525 DOI:
10.1021/acs.joc.1c00932]
[Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
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The anodic oxidation
of 1-butyl-3-methylimidazolium tetrafluoroborate
(BMIm-BF4) efficiently generates BF3 from BF4–. This Lewis acid, strongly bound to the
ionic liquids, can be efficiently used in classical BF3-catalyzed reactions. We demonstrated the BF3/BMIm-BF4 reactivity in four reactions, namely, a domino Friedel–Crafts/lactonization
of phenols, the Povarov reaction, the Friedel–Crafts benzylation
of anisole, and the multicomponent synthesis of tetrahydro-11H-benzo[a]xanthen-11-ones. In comparison
with literature data using BF3-Et2O in organic
solvents, in all the presented cases, analogous or improved results
were obtained. Moreover, the noteworthy advantages of the developed
method are the in situ generation of BF3 (no storing necessity) in the required amount, using only the electron
as redox reagent, and the recycling of BMIm-BF4 for multiple
subsequent runs.
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