Metal complex catalyzed functionalization of naturally occurring monoterpenes: oxidation, hydroformylation, alkoxycarbonylation~+

摘要

Selective oxidation, hydroformylation and alkoxycarbonylation of monoterpenes, i.e, limonene, alpha-pinene, beta-pinene, and camphene, via homogeneous catalysis by metal complexes were studied. "Pd(II)+reversible co-oxidant (CuCl_2 or LiNO_3)" systems were applied for the oxidation of monoterpenes with dioxygen. Hydrogen peroxide was also used as a final oxidant in the presence of the catalytic amounts of Pd(OAc)_2 or Pd(OAc)_2/benzoquinone. The Rh and Pt/Sn systems with various achiral and chiral diphosphines as ligands were applied for the hydroformylation of monoterpenes and the PD/Sn/phosphine(diphosphine) systems for the alkoxycarbonylation, which provided the carboxylic acid derivatives. It was found tht in all systems the starting monoterpenes as well as the primarily formed products can undergo various concurrent tranformations, such as isomerization, hydrogenation, cyclization, addition, with the balance between the reaction pathways being delicate. Efforts were made to investigate the effects of the reaction variables and the catalyst composition on the product distribution in order to find the most favorable conditions for selective syntheses. Stereochemistry of the products was also studied.