A Mild, Catalytic, and Highly Selective Method for the Oxidation of α,β-Enones to 1,4-Enediones

A new and simple method is described for the one-step oxidation of alpha,beta-enones to 1,4-enediones in good yields (generally 80-90%) using t-butylhydroperoxide as stoichiometric oxidant and 20% Pd(OH)2 on carbon (5 mol %) as catalyst in CH2Cl2 solution. The same reagents have been used to convert ethylene ketals of alpha,beta-enones to the corresponding monoethylene ketals of 1,4-enediones. Seven representative examples are presented in Table 1. All of the available evidence on these oxidations points to a radical-chain mechanism initiated by the tert-butylperoxy radical (see Scheme 1). gamma-tert-Butylperoxy ethers are formed as major products in the oxidation of alpha,beta-enones possessing only a single gamma-hydrogen.