| Abstract
| - The addition of alcohols to vinyl ketones is catalyzed by several palladium(II) coordination complexes. The alcohol adds to the β-carbon selectively to produce ethers. The catalytic cycle involves external nucleophilic attack of the alcohol on the η2-olefin complex.
- Palladium(II) coordination complexes such as (CH3CN)2PdCl2, 1, catalyze the addition ofalcohols to vinyl ketones to produce ethers. During the catalytic cycle, the alcohol addsselectively to the β-carbon (anti-Markovnikov). The kinetics for the reaction of benzyl alcohol(BA) with methyl vinyl ketone (MVK) as catalyzed by 1 has been investigated in detail. Theexperimental rate law is first-order in catalyst and BA and features saturation kinetics inMVK. Acetonitrile is a competitive inhibitor for MVK. The most consistent mechanism withthe experimental findings involves substitution of an acetonitrile ligand by MVK in apreequilibrium step (K1 = 0.020 ± 0.004 in CDCl3 at 25 °C) followed by nucleophilic attackof benzyl alcohol (k2 = (7.6 ± 0.8) × 10-3 M-1 s-1 in CDCl3 at 25 °C). A kinetic isotope effecthas been noted for the reaction in the limit of saturated MVK (k2H/k2D = 2.0). MVKcoordinates to palladium affording an η2-alkene adduct. The rate constants for severalalcohols are reported; the catalytic reaction is sensitive to steric hindrance of the alcoholnucleophile: 1° > 2° ≫ 3°. Appreciable kinetic effects are observed by variation of thesubstituents on BA. Two new palladium(II) coordination complexes containing bidentateand tridentate pyridyl imine ligands have been synthesized, fully characterized, and exploredas catalysts for the hydroalkoxylation reaction. The synthesis of AgBArF4 and its use inmetathesis reactions with Pd(II) complexes are described. A mechanism has been put forthwhere the carbonyl group of the olefin interacts with palladium and directs the alcoholaddition to the β-carbon, resulting in the anti-Markovnikov addition ether product. Finally,the charge of the palladium complex augments catalytic activity.
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