N-Trifluoroacetoxyquinuclidinium trifluoroacetate was prepared in situ from quinuclidine N-oxide and (CF3CO)2O. Except for some electron-poor substrates, this reagent allows for the high-yielding oxidative trifluoroacetoxylation of 1°, 2°, and 3° benzylic C-H bonds under photocatalytic conditions. The trifluoroacetoxylation of an ibuprofen methyl ester allowed the selective functionalization of a 2° benzylic C-H bond. For alkylbenzenes, hydrogen-atom transfer from a benzylic C-H bond to a quinuclidine cation radical was proposed to be the reaction-product-determining step.
Michael Hitt, Andrei N Vedernikov. Oxidative Trifluoroacetoxylation of 1°, 2°, and 3° Benzylic C(sp3)-H Bond Donors Using N-Trifluoroacetoxyquinuclidinium Salts under Photoredox Catalysis. Organic letters. 2022 Oct 28;24(42):7737-7741
PMID: 36239346
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