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. The catalytic system involves dilute hydrogen peroxide, Na2M04 salts (M = Mo(VI), W(VI)), and Hg(OAc),. In the absence of mercuric derivative no oxidation takes place. By changing the pH of the aqueous phase and the nature of the phase transfer agent, either cationic or neutral, as well as the metal (Mo or W), carboxylic acids or a-keto aldehydes may be selectively obtained in fairly good yields.