Oxidation of Allenes and Alkynes with Hydrogen Peroxide Catalyzed by Cetylpyridinium Peroxotungstophosphate (PCWP)
摘要:
The oxidation of allenes and alkynes with hydrogen peroxide catalyzed by peroxotungstophosphate (PCWP) was examined. A variety of allenes were first converted into the corresponding alpha-ethoxy ketones upon treatment with 35% H2O2 under the influence of PCWP in a mixed solvent consisting of ethanol and dichloromethane. When the reaction was carried out using tert-butyl alcohol as a solvent, approximately a 1:1 regioisomeric mixture of alpha-hydroxy ketones was obtained along with a small amount of alpha-tert-butoxy ketone. Oxidation of internal alkynes such as 4-octyne by the PCWP-H2O2 system under phase-transfer conditions using chloroform produced alpha,beta-epoxy ketones in good yields. The same reaction in a mixed solvent of ethanol and chloroform gave alpha,beta-unsaturated ketones rather than alpha,beta-epoxy ketones. Plausible reaction paths are proposed for the oxidation of allenes and alkynes by the PCWP-H2O2 system.
The oxidation of allenes and alkynes with hydrogen peroxide catalyzed by peroxotungstophosphate (PCWP) was examined. A variety of allenes were first converted into the corresponding alpha-ethoxy ketones upon treatment with 35% H2O2 under the influence of PCWP in a mixed solvent consisting of ethanol and dichloromethane. When the reaction was carried out using tert-butyl alcohol as a solvent, approximately a 1:1 regioisomeric mixture of alpha-hydroxy ketones was obtained along with a small amount of alpha-tert-butoxy ketone. Oxidation of internal alkynes such as 4-octyne by the PCWP-H2O2 system under phase-transfer conditions using chloroform produced alpha,beta-epoxy ketones in good yields. The same reaction in a mixed solvent of ethanol and chloroform gave alpha,beta-unsaturated ketones rather than alpha,beta-epoxy ketones. Plausible reaction paths are proposed for the oxidation of allenes and alkynes by the PCWP-H2O2 system.