Direct esterification of benzylic C-H bonds with limiting C-H substrates presents an ideal strategy to access benzylic alcohols while preventing further oxidation to ketones. Here, we report a photo-promoted benzylic C(sp<sup>3</sup>)-H esterification reaction. This method overcomes two major limitations of Kharasch-Sosnovsky-inspired reactions, enabling the use of limiting C-H substrate and activation of peroxides under mild reaction conditions. Mechanistic insights reveal that blue light promotes carboxylate-to-copper charge transfer, resulting in reduction of copper(II) and regeneration of the active copper(I) catalyst. This esterification strategy provides access to secondary and tertiary benzylic alcohols useful for medicinal chemistry and related disciplines.

Photo-promoted Kharasch-Sosnovsky reaction enabling esterification of benzylic C(sp<sup>3</sup>)-H bonds

ACS Spring 2022

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Photo-promoted Kharasch-Sosnovsky reaction enabling esterification of benzylic C(sp3)-H bonds

Photo-promoted Kharasch-Sosnovsky reaction enabling esterification of benzylic C(sp³)-H bonds