Effect of substrate and catalyst chirality on the diastereoselective epoxidation of R-(+)-limonene with manganese(III) salen complexes

Abstract

The asymmetric epoxidation of R-(+)-limonene in the presence of the Jacobsen´s catalyst in its chiral and achiral either homogeneous or heterogeneous (immobilized on Al-MCM-41) forms was studied using in situ generated dimethyldioxirane as oxidizing agent. It was found that the catalytic activity of the chiral and achiral forms of the Jacobsen´s catalyst was very similar either homogeneous or heterogeneous. This result suggests that the preferential formation of cis-(+)-1,2-limonene oxide depends not only on the catalyst chiral center, but also on the substrate chiral center. This represents a clear advantage from the economical point of view since the achiral catalyst is much less expensive than its chiral counterpart.

Keywords

• R-( )-limonene
• enantiomerically pure epoxides
• asymmetric synthesis
• manganese (III) salen complexes
• optically active catalysts
• achiral catalyst