Catalytic Reductive Homocoupling of Benzyl Chlorides Enabled by Zirconocene and Photoredox Catalysis

The bibenzyl skeleton is prevalent in numerous natural
products
and other biologically active compounds. Radical homocoupling provides
a straightforward approach for synthesizing bibenzyls in a single
step with the reductive homocoupling of benzyl halides undergoing
extensive development. Unlike benzyl bromides and other tailored precursors
used in visible-light-mediated homocoupling, benzyl chlorides offer
greater abundance and chemical stability. Nevertheless, achieving
chemoselective cleavage of the C–Cl bond poses significant
challenges, with only a limited number of studies reported to date.
Herein, we demonstrate a catalytic reductive homocoupling of benzyl
chlorides facilitated by zirconocene and photoredox catalysis. This
cooperative catalytic system promotes C–Cl bond cleavage in
benzyl chlorides under mild conditions and supports the homocoupling
of a wide range of benzyl chlorides, including those derived from
pharmaceutical agents. Our preliminary mechanistic investigations
highlight the pivotal role of hydrosilane in the catalytic cycle.