Efficient cyclopropanation of olefins catalyzed by ruthenium phthalocyanines
Résumé
Carbene transfer reactions catalyzed by metal complexes are widely used in organic chemistry [1]. Due to high versatility of this synthetic strategy involving metal carbene complexes, a large range of elaborated compounds can be prepared via cyclopropanation of olefins and carbene insertion into C-H, N-H and O-H bonds [1,2]. Among the metal complexes, metalloporphyrins have been extensively studied as catalysts for the carbene transfer reactions [3]. In contrast, their phthalocyanine counterparts have been rarely used [4]. We present here the first detailed study of the application of several ruthenium phthalocyanine complexes for the large-scope intermolecular cyclopropanation of olefins. The influence of the phthalocyanine structure, the nature of carbene precursor and olefin substrate on the efficiency of cyclopropanation reaction was investigated. Kinetic and spectroscopic studies suggest the involvement of dicarbene active complex which provides high yields of cyclopropanation products (up to 100 %) with high trans/cis ratio (up to 6.0). The structure of active species and the mechanism of cyclopropanation will be discussed.