Cross-Double Deoxygenative Carbon-Carbon Bond Formation between Benzyl Benzoates and Allylic Alcohols

Carbon-carbon (C-C) bond formation reactions play a pivotal role in organic synthesis. Cross-coupling reactions are powerful tools for forging C-C bonds. One of the major challenges in this field is to use readily available functional groups as coupling partners. The cross-coupling utilizing alcohols and their derivatives as coupling partners is particularly appealing due to their abundance in both natural and commodity chemicals, low toxicity, stability, and cost-effectiveness. Nevertheless, the cross-double deoxygenative coupling between two alcohols or their derivatives remains underdeveloped. Herein, we report a cross-double deoxygenative carbon-carbon (C-C) bond formation between benzyl benzoates and allylic alcohols through photoredox catalysis. Primary, secondary, and tertiary benzyl benzoates bearing an electron-withdrawing group at the para-position and fluorenyl benzoate are suitable for coupling with both linear and cyclic allylic alcohols. Various benzylic allylated products can be prepared with remarkable functional group compatibility, owing to the mild and external oxidant or reductant-free conditions. Control experiments indicated that the reaction proceeds through a radical coupling pathway. Density functional theory (DFT) calculations suggest that the iron additive plays a key role as the sustained-release agent in regulating the rate of benzyl radical formation, thereby preventing the formation of hydrodeoxygenative and deoxygenative dimerization products of the benzoates.