Photocatalyzed Benzylic Fluorination: Shedding “Light”
on the Involvement of Electron Transfer
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Abstract
The
photocatalyzed oxidation of benzylic compounds by 1,2,4,5-tetracyanobenzene
(TCB) in the presence of Selectfluor provides a synthetically efficient
route to electron deficient, less substituted, and otherwise inaccessible
benzylic fluorides. The virtue of this system is multifold: it is
metal-free and mild, and the reagents are inexpensive. Mechanistically,
the data suggest the intimate formation of intermediate radical cations
in the key radical forming step, as opposed to a concerted hydrogen
atom transfer process