Studies on olefin epoxidation with t-BuOOH catalysed by dioxomolybdenum(VI) complexes of a novel chiral pyridyl alcoholate ligand

The chiral dioxomolybdenum(VI) complexes [MoCl{(1R,2S,5S)-8-trimethylsilylo xy-1-(2-pyridyl)mentholato}(O)(2)-(THF)] and [Mo{(1R,2S,5S)-8-trimethylsily loxy-1-(2-pyridyl)mentholato}(2)(O)(2)] have been prepared in good yields b y reaction of the solvent substituted complex [MoCl2O2(THF)(2)] with one or two equivalents of chiral 2'-pyridyl alcohol. The optically active aminoal cohol was obtained by reaction of 2-pyridyllithium with (-)-(2S,5S)-8-trime thyl-silyloxymenthone. The complexes are active catalysts in the homogeneou s epoxidation of cyclic and linear olefins, dienes and terpenes by t-BuOOH. They present remarkable activity and excellent product selectivity in cycl ooctene epoxidation (cyclooctene oxide was obtained in quantitative yield). In the case of limonene, regioselectivity is high in favour of the epoxida tion of the internal cyclic double bond. Ring opening activity was also obs erved for alpha -pinene oxide, producing campholenic aldehyde and epoxy cam pholenic aldehyde.