Transition metal salts mediated oxidative radical addition of ethyl acetoacetate to limonene

transition metal salts mediated oxidative radical addition of ethyl acetoacetate to limonene produced chemo- and regiospecificaly (1'R, 5RS)-3-carboethoxy-2,5-dimethyl-5-(4'-methylcyclohexen-3'-enyl)-4,5-dihydrofuran as a 1:1 mixture of diastereoisomers. The best yield (72% isolated) was obtained using limonene (1 mot equiv.), ethyl acetoacetate (1 mol equiv.) and Mn(OAc)(3). 2H(2)O (2 mol equiv.) in acetic acid at 70 degreesC. The utilisation of cerium(IV) ammonium nitrate (CAN) or Co(OAC)(2) instead of Mn(III) led to lower yields of the dihydrofurans along with diethyl 2,3-diacetylsuccinate. Fe(III) salts gave a complex mixture of products and using CuCl2 there was no reaction.