A catalyst system and process for the oxidative cleavage of alkenes with hydrogen peroxide is provided. The catalyst system comprises a source of ruthenium, a source of molybdenum and a phase transfer agent. The process comprises contacting an alkene with the hydrogen peroxide in the presence of the above catalyst system. Sources of ruthenium and molybdenum comprise the metals, salts or complexes. Preferred sources are RuCl.sub.3 and MoO.sub.3. The phase transfer agent is preferably a quaternary ammonium salt. The process usually takes place in the presence of an organic solvent, preferably t-butanol.