KINETICS AND MECHANISM OF THE DIHYDROXYLATION AND EPOXIDATION OF CONJUGATED DIENES WITH HYDROGEN-PEROXIDE CATALYZED BY METHYLRHENIUM TRIOXIDE

The title reactions occur readily. With acetonitrile chosen as the sol vent, 17 of them were studied by kinetic methods. As is true for other MTO-catalyzed reactions, peroxorhenium complexes are the active speci es. Under the conditions of hydrogen peroxide present in large excess, usually employed here, CH3Re(O)(eta(2)-O-2)(2)(OH2) was the major rea ctive catalyst present: The rate constant between it and the dienes in crease or decrease as substituents add or remove electron density from the C=C bonds, suggesting a concerted mechanism in which the double b ond attacks a peroxide oxygen. Many of the products are diols; some re arranged, except when the stability of carbocation intermediates for e poxide ring opening are so unstable as to prolong their lives. When ur ea-hydrogen peroxide was used instead, the monoepoxides were obtained.