Pergamon 0040-4020(95)01026-2 Tetrahedron, Vol. 52, No. 10, pp. 3659-3668, 1996 Copyright O 1996 ElsevierScienceLtd Printed in Great Britain. All rights reserved 0040-4020/96 $15.00 + 0.00 KF Adsorbed on Alumina Effectively Promotes the Epoxidation of Electron Deficient Alkenes by Anhydrous t-BuOOH! Veejendra K. Yadav* and Kamal K. Kapoor Department of Chemistr3', Indian Institute of Technology, Kanpur 208 016, India e-mail: vijendra@iitk.ernet.in Abstract. KF adsorbed on alumina (KF-AI203) has been studied in detail for the epoxidation of electron deficient alkenes with anhydrous t-BuOOH. Aqueous base sensitive functional groups survive the reagent. Cyclopentenones are oxidized in decent to quantitative yields without showing any observable aldol products. ~l~,,/,~-Dienonesare regioselectively oxidized at the et,[$-position. Unlike aqueous alkaline H202, KF-AI203 is non-stereospecific and offers a mixture ofcis and trans oxides from most acyclic enones. Except for the oxidation of a,~-unsaturated lactones and for the difference in reaction rates, the present reagent is, in general, sirmlar to the t-BuOOH-DBU combination. Genesis Epoxidation of electron deficient alkenes is an often encountered chemical reaction. The resulting oxiranes are readily transformed into various useful materials, e.g., c~- and ffhydroxy carbonyl compounds I , ~,13-epoxy alcohols 2, allylic alcohols 3, and 1,3-diols4; among others. Nucleophilic c~- and Wopenings of the oxirane ring enhance their utility further 5. The a- and Whydroxy carbonyl groupings are present in various natural products including mevinolins. In connection with a programme directed at the synthesis of mevinolin analogs for their pharmacological evaluations, we became interested in the oxidation of 6-substituted 3,4-dehydro-2- oxotetrahydropyran, We first attempted the epoxidation of 3,4-dehydro-6-(2-phenylethyl)-2-oxotetrahydropyran (hereinafter refered to as either 'lactenone' or 'enelactone') with alkaline hydrogen peroxide under conditions of Trost 6 and Payne 7a. The reaction was very slowS; lactone ring opening was prominent and methyl 2,3-epoxy-5-hydroxy-7- phenyl-2-heptanoate was the major product. The desired oxirane was formed in only small amounts. Substituting MeOH by other water-miscible and yet non-nucleophilic solvents such as THF and DME were completely ineffective; only the starting enelactone was isolated in each instance. The reaction using Triton-B as base and t-BuOOH as the oxidant in benzene 4 resulted in an intractable products mixture. The reaction, at reflux, with excess m-CPBA (6 equiv) in dichloroethane 9 for 6h furnished a mixture of the desired oxirane and the unreacted lactenone. Although the unreacted m-CPBA was still present, the conversion to oxirane was only 60%. Moreover, product separation from the unreacted lactenone by gravity column chromatography was tediousl o. We did not use alkylzinc alkylperoxides I l as they are very chemoselective and bring about the oxidation of enones only. Although no cyclic examples were studied by the original authors, the application of Dedicated to the sweet memory of Mr. Avaneesh Yadav on the sad ooc~mon of his first death a n m v ~ . 3659