Cyclohexyl metaborate

Cyddhexylidenecarbene, 30 Cydohexyl iodide, 557 Cyclohexyl metaborate trimer, 112... 

Epoxidation.2 The reaction of tetralin hydroperoxide (cumene, cyclohexyl, and /-butyl hydroperoxides were also used, but to a lesser extent) with cyclohexyl metaborate (This volume)3 in the presence of an olefin results in formation of an epoxide from the olefin and generation of tetralol. The new reagent is very similar in behavior to penoxyacids. Transient hydroxonium ions, OH+, are postu-... 

Any alkyl metaborate ester can be used cyclohexyl metaborate is easily prepared and is soluble in organic solvents. 

Cyclohexyl metaborate activates alkyl peroxides so that the combination provides effective epoxidizing agents (52). A good arrangement of soft-hard fragments ready for transfer of an oxygen to olefins is shown. The harder phenyl metaborate reacts with the hydroxy oxygen of tetralin hydroperoxide (53). 

Alkyl metaborate esters in combination with organic hydroperoxides are reported to be active for epoxidation [182]. The borate esters are cyclic and have general formula (ROBO)3, where R is an alkyl group like cyclohexyl (CeHn). They are six-membered ring compoimds formed from O-B units with a pendant RO, and are 1 1 dehydro adducts of alcohol and boric acid. 

The metaboric acid is fed to the oxidation train continuously and the mole ratio of boron added to O2 utilized is kept in the 0.65 to 1 range. The primary role of the metaboric acid is to esterify the cyclohexanol, thereby preventing selectivity robbing overoxidation. The boric acid also serves to catalyze the de-peroxidation of the cyclohexylhydroperoxide to cyclohexanol in high yield (-95%) at the expense of other uncatalyzed decomposition products such as cyclohexanone. This effect arises from the ability of the boron compound to reduce the intermediate hydroperoxide to the corresponding cyclohexyl borate ester, dioxygen, and water (Scheme l)M... 

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