Chaykovsky Epoxidation and Cyclopropanation

During the total synthesis of (+)-phyllanthocin, A.B. Smith and co-workers installed the epoxide functionality chemo-and stereoselectively at the C7 carbonyl group of the intermediate diketone by using dimethylsulfoxonium-methylide in a 1 1 solvent mixture of DMSO-THF at 0 °C. The success of this chemoselective methylenation was attributed to the two a-alkoxy substituents, which render the C7 carbonyl group much more electrophilic than Cl 0. 

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. 

One of the steps in the highly stereoselective total synthesis of ( )-isovelleral involved the cyclopropanation of an a, 3-unsaturated ketone using dimethylsulfoxonium methylide. C.H. Heathcock and co-workers studied this transformation under various conditions and they found that THF at ambient temperature gave superior results to DMSO, which is the most common solvent for the Corey-Chaykovsky cyciopropanation. 

---

Related reactions Corey-Chaykovsky epoxidation and cyclopropanation ... 

---