MECHANISM OF THE WACKER PROCESS - STEREOCHEMISTRY OF THE HYDROXYPALLADATION

The stereochemistry of hydroxypalladation, the first step in the Wacker oxidation of ethylene to acetaldehyde, was determined using cis-1,2-dideuterio ethylene by intercepting the intermediate β-hydroxyethylpalladium complex with carbon monoxide. The formation of trans-2,3-dideuterio-β-propiolactone from cis-1,2-dideuterioethylene under the Wacker reaction conditions demonstrated that the hydroxypalladation step proceeded stereo-specifically trans. The reaction of propene under the same conditions resulted in the formation of 4-methyl-oxetanone and acetone, demonstrating that the Wacker oxidation and carbonyl insertion were competitive. Other olefins such as butene, and pentene afforded only the ketone oxidation products. © 1979.