Transition Metal‐Catalyzed Cross‐Couplings of Benzylic Sulfone Derivatives

In recent years, the use of organosulfones as a new class of cross‐coupling partner in transition‐metal catalyzed reactions has undergone significant advancement. In this personal account, our recent investigations into desulfonylative cross‐coupling reactions of benzylic sulfone derivatives catalyzed by Pd, Ni, and Cu catalysis is described. Combined with the facile α‐functionalizations of sulfones, our methods can be used to form valuable multiply‐arylated structures such as di‐, tri‐, and, tetraarylmethanes from readily available substrates. The reactivity of sulfones can be increased by introducing electron‐withdrawing substituents such as 3,5‐bis(trifluoromethyl)phenyl and trifluoromethyl groups, which enable more challenging cross‐coupling reactions. Reactive intermediates including Cu‐carbene complexes were identified as key intermediates in sulfone activation, representing new types of C−SO2 bond activation processes. These results indicate sulfones are powerful functional groups, enabling new catalytic desulfonylative transformations. In this personal account, we describe our recent progress in transition‐metal‐catalyzed cross‐coupling reactions of benzylic sulfones through carbon‐sulfonyl bond activation. Utilizing a sulfonyl group as a transient directing group, modular and straightforward synthesis of multiply‐arylated structures from readily available substrates is established.