Catalytic Asymmetric Epoxidation and Kinetic Resolution: Modified Procedures Including in Situ Derivatization

Yun Gao, K. Barry Sharpless, Janice M. Klunder, Robert M. Hanson, Soo Y. Ko, Hiroko Masamune

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Abstract

The use of 3A or 4A molecular sieves (zeolites) substantially increases the scope of the titanium(IV)-catalyzed asymmetric epoxidation of primary allylic alcohols. Whereas without molecular sieves epoxidations employing only 5 to 10 mol % Ti(0-/-Pr)4generally lead to low conversion or low enantioselectivity, in the presence of molecular sieves such reactions generally lead to high conversion (>95%) and high enantioselectivity (90-95% ee). The epoxidations of 20 primary allylic alcohols are described. Especially noteworthy are the epoxidations of cinnamyl alcohol, 2-tetradecyl-2-propen-l-ol, allyl alcohol, and crotyl alcohol—compounds which heretofore had been considered difficult substrates for asymmetric epoxidation. In the case of allyl alcohol, the use of cumene hydroperoxide substantially increases both the reaction rate and the conversion, even in the absence of molecular sieves. In general, enantioselectivities are slightly depressed (by 1-5% ee) relative to reactions employing 50–100 mol % Ti(0-z-Pr)4. The epoxidation of low molecular weight allylic alcohols is especially facilitated and, in conjunction with in situ derivatization, provides for the synthesis of many epoxy alcohol synthons which were previously difficult to obtain. The kinetic resolution of four secondary allylic alcohols with 10 mol % Ti(0-z-Pr)4is also described. The role of molecular sieves in the reaction and the effects of variation in reaction stoichiometry, oxidant, and tartrate are discussed.

Original languageEnglish
Pages (from-to)5765-5780
Number of pages16
JournalJournal of the American Chemical Society
Volume109
Issue number19
DOIs
StatePublished - 1 Sep 1987

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