Mn(III)-tetraarylporphyrins bearing covalently bonded crown-ethers: Synthesis and catalytic activity in 1-dodecene epoxidation promoted by aqueous HOCl/OCl(-)

Mn(III)-complexes of tetraarylporphyrins 1-4 bearing a crown-ether covalently linked through a single flexible chain have been synthesized. Their basic frame is that of the robust tetra-(2,6-dichlorophenyl)porphyrin 5 and the chain is connected by ether linkage either to the ortho (1-2) or to the meta positions (3-4) of one meso-aryl group. Catalytic efficiency was tested in the epoxidation of the poorly reactive 1-dodecene at 0 degrees C under CH2Cl2/H2O two-phase conditions in the presence of NaOCl (pH 9.5-10.0) as oxygen donor. The results obtained led us to propose a general acid/base catalysis as an explanation for the positive effect of crown-ethers in the alkene epoxidations with this catalytic system.