Ni-Catalyzed Reductive Coupling of Acetals with Anhydrides and Vinyl Triflates via Single-Electron C–O Activation: A Polarity-Convergent Approach to Native and Umpolung Aldehyde Reactivity

We report a Ni-catalyzed reductive cross-coupling of benzaldehyde-derived acetals with acyl anhydrides or vinyl triflates that provides modular access to α-substituted ethers. A Lewis acid and a zinc reductant convert the acetal substrates to α-oxy alkyl radicals, which undergo selective C(sp3)-C(sp2) bond formation mediated by a Ni catalyst. This catalytic method delivers ether-variants of the benzoin condensation and Nozaki-Hiyama-Kishi (NHK) reaction of aldehydes under a single set of reductive conditions, delivering a polarity-convergent approach to two classic but polarity-distinct reactions of aldehydes. The methodology exhibits a broad substrate scope, accommodating diverse anhydrides, vinyl triflates and benzaldehyde dimethyl acetal derivatives. Changing the identity of the Lewis acid activator was critical to expanding the acetal scope from dimethyl to dialkyl acetal derivatives. Stoichiometric, organometallic and spectroscopic studies were conducted to interrogate the reaction mechanism.