The invention relates to a catalytic system for use in a process for the preparation, in a single step, of enones by an aldol condensation of a ketone, such as a gem-dimethyl cyclohexylethanone or gem-dimethyl cyclohexenylethanone derivative, with an aldehyde in the presence of a novel catalytic system and a co-ingredient, such as a carboxylic acid anhydride or an anhydrous salt, and without the pre-formation of an enolate. The catalytic system is a metal complex, such as a [(Cl).sub.n(alkoxy).sub.4-nTi] or [(Cl).sub.n(alkoxy).sub.4-nZr] complex where n is 1 to 3.