Abstract |
A series of phthalocyanine (Pc) complexes of general formula (M(Pc)) (M = Mg, V, Mn, Fe, Co, Ni, Cu, Zn) was tested as catalysts for functionalization of sp(3) C-H bonds, namely in the mild stereoselective oxidation of cyclic alkanes (isomers of dimethylcyclohexane and decahydronaphthalene) using peroxides as oxidants. A high catalytic activity (yield of products up to 75\% based on the oxidant) and outstanding retention of stereo configuration of substrates (> 95\% for isomers of dimethylcyclohexane) was disclosed for the cobalt phthalocyanine catalyst [Co(Pc)] using m-chloroperbenzoic acid (m-CPBA) as oxidant and nitric acid as promoter. The phthalocyanine complexes other than Co are much less active with yields of products < 10\% and low stereo- and bond selectivities. The main reaction mechanism is proposed not to involve high-valent metal species, as evidenced by O-18-labeling and selectivity studies. The [Co(Pc)]/HNO3/m-CPBA system also catalyses chlorination and bromination of cyclohexane with HCl and N-bromosuccinimide as halogen sources. |