Studies on olefin epoxidation with t-BuOOH catalysed by dioxomolybdenum(VI) complexes of a novel chiral pyridyl alcoholate ligand
作者:Anabela A. Valente、Isabel S. Gonçalves、Andre´ D. Lopes、Jose´ E. Rodríguez-Borges、Martyn Pillinger、Carlos C. Romão、João Rocha、Xerardo García-Mera
DOI:10.1039/b102523f
日期:——
The chiral dioxomolybdenum(VI) complexes [MoCl(1R,2S,5S)-8-trimethylsilyloxy-1-(2-pyridyl)mentholato}(O)2(THF)] and [Mo(1R,2S,5S)-8-trimethylsilyloxy-1-(2-pyridyl)mentholato}2(O)2] have been prepared in good yields by reaction of the solvent substituted complex [MoCl2O2(THF)2] with one or two equivalents of chiral 2′-pyridyl alcohol. The optically active aminoalcohol was obtained by reaction of 2-pyridyllithium with (−)-(2S,5S)-8-trimethylsilyloxymenthone. The complexes are active catalysts in the homogeneous epoxidation of cyclic and linear olefins, dienes and terpenes by t-BuOOH. They present remarkable activity and excellent product selectivity
in cyclooctene epoxidation (cyclooctene oxide was obtained in quantitative yield). In the case of limonene, regioselectivity is high in favour of the epoxidation of the internal cyclic double bond. Ring opening activity was also observed for α-pinene oxide, producing campholenic aldehyde and epoxy campholenic aldehyde.
手性二氧钼(VI)配合物[MoCl(1R,2S,5S)-8-三甲基硅氧基-1-(2-吡啶基)薄荷醇配体}(O)2(THF)]和[Mo(1R,2S,5S)-8-三甲基硅氧基-1-(2-吡啶基)薄荷醇配体}2(O)2]通过溶剂取代的配合物[MoCl2O2(THF)2]与一个或两个当量的手性2′-吡啶醇反应制备得到,产率良好。通过2-吡啶基锂与(−)-(2S,5S)-8-三甲基硅氧基薄荷酮的反应得到光学活性氨基醇。这些配合物作为t-BuOOH存在下环状和直链烯烃、二烯和萜烯的均相环氧化反应的活性催化剂。它们在环辛烯环氧化反应中表现出显著的活性和优异的产品选择性(环辛烯氧化物以定量产率获得)。在柠檬烯的情况下,区域选择性较高,有利于内部环双键的环氧化。还观察到α-蒎烯氧化物的开环活性,生成蒎烯醛和环氧蒎烯醛。