类叶绿素镁卟啉高效催化CO_2环_省略_应无溶剂合成氯丙烯碳酸酯_英文_王梅

CATALYSIS, KINETICS AND REACTORS Chinese Journal of Chemical Engineering, 19(3) 446—451 (2011)

Efficient Solvent-free Synthesis of Chloropropene Carbonate from the Coupling Reaction of CO2 and Epichlorohydrin Catalyzed by

Magnesium Porphyrins as Chlorophyll-like Catalysts*

WANG Mei (王梅)1,2, SHE Yuanbin (佘远斌)1,**, ZHOU Xiantai (周贤太)2 and JI Hongbing (纪红兵)2,**

1 Institute of Green Chemistry & Fine Chemicals, Beijing University of Technology, Beijing 100022, China

2 School of Chemistry and Chemical Engineering/Key Laboratory of Low-carbon Chemistry & Energy Conserva-

tion of Guangdong Province, Sun Yat-sen University, Guangzhou 510275, China

Abstract Highly efficient solvent-free coupling reaction of carbon dioxide (CO2) and epichlorohydrin catalyzed

by meso-tetraphenyl porphyrin magnesium (MgTPP) in the presence of triethylamine as co-catalysts is reported. As a chlorophyll-like catalyst, MgTPP showed excellent activity for the coupling reaction of CO2 and epichlorohydrin to chloropropene carbonate, in which the turnover number could reach up to 9200. Moreover, different factors in-cluding the amount of catalyst, reaction temperature, pressure and time were systematically investigated and the op-timal reaction conditions were obtained (epichlorohydrin 50 mmol, MgTPP 5.0×10−3 mmol, triethylamine 6.25×10−3 mmol, 140 °C, 1.5 MPa, 8 h). A plausible two-pathway mechanism for the coupling reaction of CO2 and epichlorohydrin is proposed to propound the catalysis of MgTPP. Keywords magnesium prophyrin, chlorophyll-like, epichlorohydrin, carbon dioxide

1 INTRODUCTION Recently the chemical fixation of carbon dioxide (CO2) draws much attention from the viewpoint of carbon resources and environmental problems [1-3]. Fundamental study on the activation and fixation of CO2 has made much progress in recent years, in which the most successful example is the atom-economy coupling reaction of CO2 and epoxides to generate cyclic carbonates [1, 4]. Numerous catalyst systems have been developed for this transformation, including simple alkali metal salts [5-7], ionic liquids [8, 9], am-monium salts [10, 11] and transition metal complexes [12, 13]. While the advances have been significant, most of these catalysts usually suffer from drawbacks such as low catalytic activity/selectivity, large amount of catalyst or severe reaction conditions. As biomimetic catalysts, metalloporphyrins could be used as an intermediate of oxygen carrier for bio-logical systems, and have been widely used as cata-lysts for various oxidation reactions [14]. As model catalysts cytochrome P-450, metalloporphyrins were commonly used for dioxygen activation in oxidation of organic compounds.[15, 16] However, several cata-lytic systems of the coupling reaction of CO2 and ep-oxides catalyzed by metalloporphyrins in the presence of nucleophiles such as N,N-dimethylaminopyridine (DMAP) have been developed. [17-19] Jin et al. re-ported that cobalt porphyrins could efficiently catalyze the coupling reaction of CO2 and epoxides with phenyl-trimethylammonium tribromide (PTAT) as co-catalysts, in which the highest turnover number (TON) of cata-lyst was 900. [20] Paddock et al. reported cobalt por-

phyrin catalytic system [CoTPPCl/TEA, (triethyl-amine)] was also efficient for the coupling reaction of CO2 and epoxides, the TON could be 1947 when the

reaction was conducted for 22.5 h [17].

It is well known that chlorophyll in photosynthe-sis has been providing the essential food and energy for human beings by transforming CO2 and water into

carbohydrate compounds in organism. [21] Meanwhile,

chlorophyll is a significant metalloporphyrin deriva-tive, and the structural active site of chlorophyll is magnesium porphyrins. Therefore, the simulation of the performance of chlorophyll for achieving CO2

fixation is of great significance, and it might provide a

new CO2 fixation method by biomimetic route.

In our previous studies, a series of efficient cata-lytic systems for the metalloporphyrins-catalytic aero-bic oxidation of cyclohexane [22], p-nitrotoluene [23, 24],

olefin [25], sulfide [26], alcohol [27], ketone [28] etc.

have been developed. Based on successive research on the biomimetic process learnt from the nature [29],

herein an efficient solvent-free coupling reaction of CO2 and epichlorohydrin catalyzed by meso-tetraphenyl

porphyrin magnesium (MgTPP) as chlorophyll-like catalysts has been developed (Fig. 1), in which the TON reached as high as 9200. Besides, a novel combined