Synthesis of α-Quaternary Aldehydes via a Dual Ni/Rh-Catalyzed Tandem Isomerization–Propargylation Reaction

A dual Ni/Rh catalysis sequence toward α-quaternary aldehydes is reported. An intramolecular approach from allyl propargyl carbonates alongside the intermolecular transformation from allylic alcohols and propargyl carbonates is described. Initial decarboxylative oxidative addition into the propargyl group by nickel generates the electrophilic Ni–allenyl species, and the resulting allylic alkoxide is isomerized into the nucleophilic Rh–enolate species. Upon recombination, the α-propargylated aldehyde is obtained. Preliminary enantioselective results are reported, with varying protocols using either a dual metal single ligand or a dual metal dual ligand system.