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US 6,686,483 B2Granted
Catalytic asymmetric epoxidation
AssigneeColorado State University Research Foundation
InventorYian Shi
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AssigneeColorado State University Research Foundation
InventorYian Shi
Estimating the term…
The present invention provides a variety of methods that are based on stereoselective epoxidation of an olefin by an epoxidizing agent derived from a reaction between an oxidizing agent and a chiral ketone. For example, present invention provides methods for producing an epoxide from an olefin, for increasing a relative concentration of at least one stereoisomer of an olefin, and for stereoselectively producing an α-acyloxy carbonyl compound. Preferably, the chiral ketone is of the formula: or a derivative thereof which is capable of converting to the chiral ketone of Formula I under the reaction conditions, where a, b, n, X, R1, R2, R3, R4, R5 and R6 are those defined herein.
A method of producing an epoxide from an olefin comprising:
A method for stereoselectively producing an α-acyloxy carbonyl compound from an enol ester olefin comprising:
A method for increasing a relative concentration of at least one stereoisomer of a compound having at least one olefinic moiety, from a stereoisomer mixture of the compound, said method comprising:
Dependencies are inferred from the claim text.
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In which the condensed system contains two hetero rings: spiro-condensed systems
Asymmetric syntheses
Separation of optically-active compounds
By modifying the hydroxylic moiety of the ester, such modification not being an introduction of an ester group: by isomerisation; by change of…
Term ended 6 Apr 2019 (estimated)
The present invention is directed to a catalytic asymmetric epoxidation of olefins by contacting an oxidizing agent to a mixture of a cyclic chiral ketone and an olefin.
Epoxides are very important chiral building blocks for the synthesis of enantiomerically pure complex molecules. Asymmetric epoxidation of olefins presents a powerful strategy for the synthesis of enantiomerically enriched epoxides. Great success has been achieved in the epoxidation of allylic alcohols, unfunctionalized cis-olefins, and conjugated trisubstituted olefins. However, the epoxidation of trans-olefins bearing no allylic alcohol group with high enantiomeric excess still remains a challenging problem.
Among many other powerful epoxidation methods chiral dioxiranes generated in situ from an oxidizing agent, typically Oxone® (potassium peroxomonosulfate), and a chiral ketone have appeared to be promising reagents for asymmetric epoxidations, particularly for trans-olefins bearing no allylic alcohol groups. Since the first asymmetric epoxidation of olefins with dioxirane were reported in 1984, significant progress has been made in the area. A C2 symmetric cyclic chiral ketone derived from 1,1′-binaphthyl-2,2′-dicarboxylic acid has been used as a catalyst to achieve high enantioselectivity for the epoxidation of trans-4,4′-disubstituted stilbenes. This cyclic chiral ketone, however, is limited to certain substrates.
FIG. 1 illustrates a synthetic scheme for a preparation of a ketone derived from D-fructose which is a useful catalyst for the asymmetric epoxidation of olefins as described in the present invention and a synthetic scheme for a preparation of L-fructose from L-sorbose;
FIG. 2 is a plot of % conversion of trans-β-methylstyrene against pH of the epoxidation reaction using 3 equivalents of acetone as the catalyst in H2O—CH3CN (1:1.5, V/V) solvent system at different time intervals;
FIG. 3 is a plot of % conversion of trans-β-methylstyrene against pH of the epoxidation reaction using 20 mol % of ketone 1 at 0° C. at 1.5 h reaction time;
“Alkyl” refers to straight or branched aliphatic hydrocarbons. Alkyl groups optionally can be substituted with one or more substituents, such as aryl and cycloalkyl. Exemplary alkyl groups include methyl, ethyl, i-propyl, propy, n-butyl, t-butyl, n-pentyl, hexyl, heptyl, octyl, and the like.
The term “alkylene” means a linear saturated divalent hydrocarbon radical of one to six carbon atoms or a branched saturated divalent hydrocarbon radical of three to six carbon atoms, e.g., methylene, ethylene, propylene, 2-methylpropylene, pentylene, and the like.
“Haloalkyl” refers to an alkyl moiety as defined herein in which one or more hydrogen atoms have been replaced with same or different halides. Exemplary haloalkyls include —CH2Cl, —CH2F, —CF3, —CH2CF3, —CH2CCl3, and the like. Moreover, haloalkyl also includes perfluoroalkyls in which all alkyl hydrogen atoms are replaced by halides.