关键词: 乙酰丙酮钴; 硅胶; 催化氧化; 单萜烯; 分子氧

Abstract:

Selective oxyfunctionalization of monoterpenes is an interesting route to utilize these inexpensive natural products for a number of applications, such as pharmaceutical, flavor and perfumery industry as well as useful synthetic intermediates. The use of solid materials in catalytic oxidations in the liquid-phase has recently been extensively investigated because of their easy recovery and the possibility of regeneration which results in a reduction of the environmental impact. In this work, a new heterogeneous catalyst Co(acac)₂/SiIm was prepared with supporting Co(acac)₂ on silica gel modified with 3-chloropropyltrimethoxysilane and imidazole, and the structure of catalyst was characterized by IR, UV-Vis and ICP-AES. Oxidation reactions of limonene, α-pinene and β-pinene with dioxygen in acetonitrile solutions containing catalytic amounts of Co(acac)₂/SiIm were studied. The results show that the higher conversion and products chemoselectivities were obtained. Limonene and α-pinene gave epoxides as predominant products with chemoselectivities 62% and 79% at 58% and 72% conversion, respectively. On the other hand, β-pinene gave allylic oxides as major products with chemoselectivity 85% at a 55% conversion rate. In addition, the reaction mechanism and competition were simply discussed.

Key words: Acetylacetone cobalt(Ⅱ); Silica gel; Catalysis oxidation; Monoterpenes; Oxygen