Palladium(II) catalyzed oxidation of naturally occurring terpenes with dioxygen

Limonene can be efficiently and selectively oxidized by dioxygen at 60-80 degrees C in glacial acetic acid containing LiCl, in the presence of the PdCl2-CuCl2 catalytic combination, giving rise to the formation of trans-carveyl acetate as the major product. Several concurrent transformations of limonene occur in the reaction solutions, i.e., isomerization, acetic acid addition, and allylic oxidation. The effect of the reaction variables on the product distribution and reaction rate has been studied. The most favorable conditions for the carveyl acetate synthesis have been found. The reactions of alpha-pinene and beta-pinene under the same conditions yield a mixture of carveyl acetate, alpha-terpenyl acetate, bornyl chloride, and fenchyl chloride. The activity of the Pd(OAc)(2)-LiNO3 combination in the oxidation of limonene, alpha-pinene, and beta-pinene has also been examined.