Phase-transfer catalytic oxidation of terminal alkynes to keto aldehydes by dilute hydrogen peroxide

A phase-transfer procedure for the oxidation of terminal alkynes under mild conditions is described. Thecatalytic system involves dilute hydrogen peroxide, Na2M04 salts (M = Mo(VI), W(VI)), and Hg(OAc),. In theabsence of mercuric derivative no oxidation takes place. By changing the pH of the aqueous phase and the natureof the phase transfer agent, either cationic or neutral, as well as the metal (Mo or W), carboxylic acids or a-ketoaldehydes may be selectively obtained in fairly good yields.