Palladium-Catalyzed Dimerization of Vinyl Ethers to Acetals

(α-Diimine)PdCl+ species catalytically dimerize alkyl and silyl vinyl ethers to β,γ-unsaturated CH2CHCH2CH(OR)2 acetals, and they cyclize divinyl ethers to analogous cyclic acetals. A plausible mechanism comprises in situ generation of an active PdOR alkoxide species, double vinyl ether insertion to generate Pd{CH2CH(OR)CH2CH(OR)2} species, and β-OR elimination to generate the acetal product. In the presence of vinyl ethers, (α-diimine)PdCl+ species can be used to initiate ethylene polymerization.