Esters methyltrioxorhenium

Methyltrioxorhenium(VII) 5 is active even at temperatures as low as -35 °C but is usually administered at 25 °C. The molybdenum(VI) catalyst requires temperatures of 80 °C (boiling benzene) to convert benzaldehyde and ethyl diazoacetate into the corresponding cinnamic ester [8]. Turnovers are not yet sufficient for technical applications but the yields range between 75 and 98% for the Recatalyzed process [9-11]. 

Key Words Ethylene oxide, Propylene oxide. Epoxybutene, Market, Isoamylene oxide. Cyclohexene oxide. Styrene oxide, Norbornene oxide. Epichlorohydrin, Epoxy resins, Carbamazepine, Terpenes, Limonene, a-Pinene, Fatty acid epoxides, Allyl epoxides, Sharpless epoxidation. Turnover frequency, Space time yield. Hydrogen peroxide, Polyoxometallates, Phase-transfer reagents, Methyltrioxorhenium (MTO), Fluorinated acetone, Alkylmetaborate esters. Alumina, Iminium salts, Porphyrins, Jacobsen-Katsuki oxidation, Salen, Peroxoacetic acid, P450 BM-3, Escherichia coli, lodosylbenzene, Oxometallacycle, DFT, Lewis acid mechanism, Metalladioxolane, Mimoun complex, Sheldon complex, Michaelis-Menten, Schiff bases. Redox mechanism. Oxygen-rebound mechanism, Spiro structure. 2008 Elsevier B.V. 

A novel class of metathesis catalysts derives from methyltrioxorhenium, CH3Re03 (MTO) [22]. Combined with certain solid supports such as Si02/Al203 or Nb205, highly active catalysts are generated [23, 24]. They even tolerate fimctional groups such as ketones, esters, and carboxylic acids. Based upon NMR spectroscopic evidence [25] and in accord with theoretical studies, surface-attached Re=CH2 species initiate metathesis via a novel type of tautomerism [Eq. (3)]. 

Activation of hydrogen peroxide has been achieved by the use of methyltrioxorhe-nium (MTO) [322]. Strukul and coworkers employed cationic platinum complexes as catalysts and hydrogen peroxide as the oxidant in the conversion of cyclohexanones into caprolactones [323]. A niobiocene complex has been applied giving esters with a regioselectivity opposite to that generally observed [324]. Some supported platinum [325], nickel [326] and methyltrioxorhenium [327] catalysts have also been used in reactions with hydrogen peroxide. 

---