The Lewis Acidic Ruthenium-Complex-Catalyzed Addition of beta-Diketones to Alcohols and Styrenes Is in Fact Bronsted Acid Catalyzed

摘要

The perchlorate salt of the dicationic bipy-ruthenium complex cis-[Ru(6,6'-Cl2bipy)2(H2O)2]~(2+) effectively catalyzes addition of beta-diketones to secondary alcohols and styrenes to yield the alpha-alkylated beta-diketones. In a catalytic addition reaction of acetylace-tone to 1-phenylethanol, the k~2-acetyla-cetonate complex [Ru(6,6'-Cl_2bipy)_2(k~2-acac)]ClO4 was isolated after the catalysis ; this complex is readily synthesizedby reacting cis-[Ru(6,6'-Cl_2bipy)_2-(H2O)2](ClO4)2 with acetylacetone. [Ru(6,6'-Cl_2bipy)_2(k~2-acac)]ClO4 is un-reactive toward 1-phenylethanol in the presence of HClO4; it also fails to catalyze the addition of acetylacetone to 1-phenylethanol. On the basis of these observations, it is proposed and confirmed by independent experiments that the catalytic addition of beta-diketones to the secondary alcohols is in fact catalyzed by the Br0nsted acid HClO4, which is generated by the reaction of cis-[Ru(6,6'-Cl_2bipy)_2(H2O)2]-(ClO4)2 with the beta-diketone.