Chaykovsky epoxidation

4 Block, E. Reactions of Organosulfur Compounds Academic Press New York, 1978. 

6 Saito, T. Akiba, D. Sakairi, M. Kanazawa, S. Tetrahedron Lett 2001, 42, 57. 

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A weak base such as glycine added to [HMIMjPFg has also been reported to catalyze a Knoevenagel reaction of malononitrile and benzaldehyde 110). A KOH-treated [BMIMjPFg also provides a suitable medium for the Corey-Chaykovsky epoxidation of enones and cyclopropanation of aldehydes using trimethyl sulfonium iodide (///). 

Scheme 6.30 Typical epoxides obtained from the Corey-Chaykovsky epoxidation of aldehydes catalyzed by urea 16.

Also, the reaction pathways of the Corey-Chaykovsky epoxidation reaction have been compared quantum-chemically <1999JOC4596>. As models for one transition state, 1,3-oxathiane compounds such as 52, suitably substituted to allow comparison with experiment (Equation 3), were calculated and these predicted both the absolute stereochemistry of the main product 53 and the distribution of the other stereoisomers, as supported by experimental results. Thus, this theoretical study was able to identify the transition state which proved to be responsible for the stereoselectivity of the catalytic Corey-Chaykovsky epoxidation reaction. 

A short enantiospecific total synthesis of (+)-aphanamol I and II from limonene was achieved and the absolute stereochemistry of I and II established in the laboratory of B. Wickberg. The key steps were a de Mayo photocycloaddition, a Corey-Chaykovsky epoxidation and finally a base-cataiyzed fragmentation of the j,8-epoxyalcohol intermediate. Upon treating the photocycloadduct with dimethylsulfoxonium methylide, only the endo epoxide diastereomer was formed due to the steric hindrance provided by the methyl and isopropyl groups. 

The conversion of a bicyclo[2.2.1]octenone derivative to the corresponding bicyclo[3.3.0]octenone, a common intermediate in the total synthesis of several iridoid monoterpenes, was achieved by N.C. Chang et al. The target was obtained by sequential application of the Corey-Chaykovsky epoxidation, Demjanov rearrangement and a photochemical [1,3]-acyl shift. 

In the laboratory of J. Mulzer, the total synthesis of laulimalide, a microtubule stabilizing antitumor agent, was accomplished. The C9 stereochemistry of the natural product was introduced using the Jacobsen HKR on a diastereomeric mixture of a terminal epoxide. The epoxide mixture was prepared via the Corey-Chaykovsky epoxidation of citronellal. The HKR proceeded in high yield and high selectivity at room temperature, and the products were easily separated by flash chromatography. The did was converted into the diastereomerically pure epoxide in three steps. 

Corey-Chaykovsky epoxidation Preparation of epoxides from aldehydes and ketones. 102... 

Related reactions Corey-Chaykovsky epoxidation and cyclopropanation ... 

The synthesis of triticonazole is only described in patents as a one-pot sequence [57] Knoevenagel condensation of 4-chlorobenzaldehyde on 2,2-dimethylcyclopentanone gives the a,) -unsaturated ketone, which enters a Corey-Chaykovsky epoxidation reaction to afford the epoxide which in turn is opened with the potassium salt of 1,2,4-triazole (Scheme 17.10). 

The synthesis scheme is described in two process patents [70] Dieckmann condensation applied to ethyl adipate leads to the salt of 2-ethoxycarbonylcyclopenta-none (Scheme 17.12). From this compound, methylation at position 2 followed by a rearrangement under basic medium brings the methyl group to position 5. The salt obtained is directly benzylated with 4-chlorobenzyl chloride. A second methylation then occurs directly at position 5 and a subsequent decarboxylation allows access to the key carbonyl cyclopentanone with all the required substituents present. The last step consists of a one-pot Corey-Chaykovsky epoxidation reaction in which are successively added to the triazolyl sodium formed in situ, the cyclopentanone and the trimethylsulfoxonium bromide. 

Other references related to the Corey-Chaykovsky epoxidation are cited in the literature. 

Corey-Chaykovsky epoxidation—additive oxidation Cyclopropanation [(1 + 2) + (1 + 2)]... 

Scheme 19.13 Organocatalytic Corey-Chaykovsky epoxidation utilising urea 9.

Three possible reaction pathways for the Corey-Chaykovsky epoxidation reaction have been compared quantum chemicallyThey all involve intramolecular attack of O on C, with an S species as leaving group. The calculations (Gaussian 94) favour... 

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