Catalytic asymmetric epoxidation and kinetic resolution: modified procedures including in situ derivatization
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(O-i-Pr)/sub 4/ generally 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-1-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 employing 50-100 mol % Ti(O-i-Pr)/sub 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(O-i-Pr)/sub 4/ is also described. The role of molecular sieves in the reaction and the effects of variation in reaction stoichiometry, oxidant, and tartrate are discussed.
- Research Organization:
- Massachusetts Institute of Technology, Cambridge
- OSTI ID:
- 5890822
- Journal Information:
- J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 109:19; ISSN JACSA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201* -- Chemical & Physicochemical Properties
ADSORBENTS
ALCOHOLS
CATALYSIS
CATALYSTS
CATALYTIC EFFECTS
CHEMICAL PREPARATION
CHEMICAL REACTION KINETICS
CHEMICAL REACTION YIELD
CHEMICAL REACTIONS
DATA
DERIVATIZATION
ELEMENTS
EPOXIDES
EXPERIMENTAL DATA
HYDROXY COMPOUNDS
INFORMATION
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
KINETICS
MATERIALS
METALS
MINERALS
MOLECULAR SIEVES
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
REACTION KINETICS
SYNTHESIS
TITANIUM
TRANSITION ELEMENTS
YIELDS
ZEOLITES