Direct C─C Bond Formation From Aldehydes via HFIP‐Assisted Hosomi‐Sakurai Methallylation

The formation of carbon-carbon bonds is a cornerstone of organic synthesis, with the Hosomi-Sakurai reaction serving as a powerful tool for introducing allyl groups to carbonyl compounds. Traditionally, this transformation relies on Lewis acid catalysis to activate the carbonyl substrate. Here, we report a solvent-assisted, catalyst-free Hosomi-Sakurai reaction of aldehydes, providing a direct, atom-economical and operationally simple route to allylated products under mild conditions at room temperature. This method exhibits broad substrate scope, including aromatic and aliphatic aldehydes, and proceeds with high chemoselectivity and functional group tolerance. Mechanistically, HFIP acts as a dual facilitator: it activates the aldehyde via hydrogen bonding, enhancing its electrophilicity, while simultaneously stabilizing the intermediate formed after allylsilane addition, thereby promoting the reaction and eliminating the need for external catalysts, additives, or Lewis acids.