Palladium-Catalyzed Dimerization of Vinyl Ethers to Acetals

Abstract

(Alpha-diimine)PdCl(+) species catalytically dimerize alkyl and silyl vinyl ethers to beta,gamma-unsaturated CH(2)=CHCH(2)CH(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{CH(2)CH(OR)CH(2)CH(OR)(2)} species, and beta-OR elimination to generate the acetal product. In the presence of vinyl ethers, (alpha-diimine)PdCl(+) species can be used to initiate ethylene polymerization.

(α-Diimine)palladium catalyzed ethylene polymerization and (co)polymerization with polar comonomers

“…Chen et al [70] also showed that (-diimine)PdCl + species catalytically dimerize vinyl ethers to CH 2 =CHCH 2 -CH(OR) 2 acetals and cyclize divinyl ethers to analogous cyclic acetals (Scheme 10). A wide variety of vinyl ethers and divinyl ethers are suitable for these transformations.…”

Recent advances in Ni-mediated ethylene chain growth: Nimine-donor ligand effects on catalytic activity, thermal stability and oligo-/polymer structure

“…Under such conditions, the hydrogen atoms belonging to the 2,6-substituted alkyl groups are in close proximity to the central metal resulting in agostic interactions with the metal ion, which ultimately leads to the deactivation of the catalytic system. On the basis of this theory, several research teams have been concerned with 8 designing new ligands sets that are capable of preventing this axial rotation of the N-aryl group.…”

“…Most notably, the α-diimine-nickel complexes first disclosed by Brookhart more than two decades ago, are highly active catalysts for the formation of high molecular weight polyethylene [2]. Furthermore, this type of catalyst produces polymers incorporating a range of branching contents and also exhibits good tolerance towards functional groups/polar monomers [3][4][5][6][7][8][9][10][11][12]. Subsequently, Brookhart [13] and Gibson [14] independently extended the range of polymerization-active late transition metals to include iron and cobalt.…”

Coupling Reaction of Enol Derivatives with Silyl Ketene Acetals Catalyzed by Gallium Trihalides

“…[2] However,t he development of ac oupling reaction using enol derivatives remains ac hallenging issue because the intrinsicf eature of inert CÀO bondsp revents the use of desirable coupling reactions. For other types of nucleophiles, such as metal enolates, only two catalyticc oupling reactions, the Pd-catalyzed dimerization of silyl vinyl ethers [8] and our reported InBr 3 -catalyzed coupling of enol ethers with ketene silyl imines, [9] have previously been achieved. For other types of nucleophiles, such as metal enolates, only two catalyticc oupling reactions, the Pd-catalyzed dimerization of silyl vinyl ethers [8] and our reported InBr 3 -catalyzed coupling of enol ethers with ketene silyl imines, [9] have previously been achieved.…”