Chengguo Sun

Investigations on the demetalation of metalloporphyrins under ultrasound irradiation.

An efficiently facile method for the demetalation from metalloporphyrins has been developed, which uses high-intensity ultrasound to initiate the ligand dissociation in a mixed solvent of (CH(3)CO)(2)O/HCl with FeSO(4). The influences of substituents, bath temperature and reaction time on the reactions were also investigated, on the base of which the mechanism of demetalation and the effect of ultrasound irradiation on metal-ligand cleavage have been discussed in detail.

Synthesis and catalytic properties of a series of cobalt porphyrins as cytochrome P450 model: the effect of substituents on the catalytic activity

A series of cobalt porphyrins derived from hemin was prepared as cytochrome P450 models. Effects of substituents at the cobalt deuteroporphyrin-propionate side chains are investigated in oxidation of toluene with air to benzaldehyde and benzyl alcohol without the use of solvent and sacrificial co-reductant. The catalytic activity of cobalt porphyrins depends on the type of substituents. When the electron-withdrawing groups like –Cl, –Br, were introduced into the double propionate side chains, they can increase the catalyst stability and selectivity to benzaldehyde. In comparison with these electron-withdrawing groups, the electron-donor groups, such as –CH3, –S–S– and –NH2 groups, can improve their catalytic activities. Moreover, the electron-donor group containing an unpaired electron (such as –S–S–, –NH2) is benefit for improving its catalytic efficiency and promoting the electron delivery. It can be concluded that the double propionate side chains in the deuteroporphyrin complex may participate in oxidation process and effect electron transfer from the high-valent metalloporphyrin species to the substrate.

Synthesis of disulfide-derivatised metallodeuteroporphyrins as novel catalysts to imitate cytochrome P 450 in the selective oxidation of cyclohexane

Metallodeuteroporphyrins with two side chains linked by a terminal cystine dimethyl ester [M(PDTEP), where M = ClFe(III), ClMn(III), Co(II)], have been synthesised. These metalloporpyirn complexes were found to act as efficient catalysts in the oxidation of cyclohexane to cyclohexanol and cyclohexanone using air as the oxygen source and in the absence of additives and solvents. The influence of the central metal, reaction temperature and pressure on the catalytic behavior of M(PDTEP) were evaluated. The high conversion and selectivity of M(PDTEP) was ascribed to the existence of intramolecular coordination by the M(PDTEP).

A convenient synthesis of haematoporphyrin ester-ethers under ultrasound irradiation

A convenient approach to the synthesis of haematoporphyrin ester-ethers from haemin under ultrasound irradiation has been developed. This method provides several advantages such as shorter reaction time, high yields and environmental friendliness.

Synthesis of Metallo-Deuteroporphyrin Derivatives and the Study of Their Biomimetic Catalytic Properties

Selective catalytic oxidations of organic molecules are among the most important technological processes in the synthetic chemistry as well as in the chemical industry for the preparation of many pharmaceuticals, vitamins, fragrances and dyestuffs (Hudlicky, 1990). However, despite great progress in organic synthesis in the last several decades, among varieties of catalysts the ones required in selective catalytic oxidations have the highest cost and the lowest selectivity, which brings the oxidation products tremendous difficulties in separation and purification (Cavani & Trifiro, 1992). On the other hand, alkanes instead of alkenes, which come from natural gas and crude oil, have gradually become the main raw materials of the chemical industry. Due to their intrinsically inert nature, the selective functionalization of alkanes is very difficult and consequently regarded as a key objective in the chemical industry (Sheldon & Kochi, 1981). Although the oxidation of alkanes is a thermodynamically favored process, it is difficult to do so in a controlled and selective fashion, since the oxidation products under the activation of oxygen atoms they involve are more active than the raw materials and prone to causing over-oxidation. Traditional oxidants such as chromates and permanganates can perform reactions of this type but are notoriously nonselective and must be used under forcing conditions. They have been discarded mainly due to their economic and environmental costs in favor of cheap oxidants such as air or peroxides, but these latter processes are extremely inefficient and require constant recycling of substrates (Costas et al., 2000). Thus increasing the efficiency and selectivity of hydrocarbon transformations, especially the activation of C—H bond of saturated hydrocarbons, has been the goal of both academic and industrial research efforts. Nature has already developed an excellent solution for the problem of the selective oxidation of organic substrates under particularly mild conditions, by utilizing as oxidant the most abundant, cheapest and cleanest one as possible, dioxygen, in the presence of metalloenzymes as catalysts (Wallar & Lipscomb, 1996; Que & Ho, 1996). Indeed, in the biological world, metal-containing proteins are able to perform oxidation reactions at room temperature under atmospheric pressure, even the hydroxylation of hydrocarbons, in spite of the relative inertness of the C—H bond in non-activated substrates. (Ricoux et al., 2007). These include non-heme enzymes, such as methane monooxygenase, which is able to