Asymmetric epoxidation of (Z)-enol esters catalyzed by titanium(salalen) complex with aqueous hydrogen peroxide |
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Authors: | Kazuhiro Matsumoto Chao FengSatoshi Handa Takuya Oguma Tsutomu Katsuki |
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Institution: | a Department of Chemistry, Faculty of Science, Graduate School, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan b International Institute for Carbon-Neutral Energy Research (I2CNER), Kyushu University, Japan c Institute for Advanced Study, Kyushu University, Japan |
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Abstract: | Titanium(salalen) complex 1 was an effective catalyst for asymmetric epoxidation of enol esters. Although (E)-enol esters were reluctant to proceed, (Z)-enol esters underwent asymmetric epoxidation to give the epoxides in high yields with high enantioselectivity ranging from 86 to >99% ee in the presence of aqueous hydrogen peroxide as the stoichiometric oxidant. Complete enantioselectivity was observed in the reaction of (Z)-3,3-dimethylbut-1-en-1-yl 4-methoxybenzoate. The obtained epoxide was readily transformed into the corresponding 1,2-diol by reduction with lithium borohydride without erosion of the high enantiomeric excess. |
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Keywords: | Asymmetric reaction Epoxidation Hydrogen peroxide Titanium Enol ester |
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