The Carbonylation Of Halohydrocarbon Catalyzed By Non-precious Metal Under Irradiation

Carbonylation is one of the essential organic synthesis processes. However, a conventional carbonylation reaction usually occurs at a high temperature and pressure in the presence of precious metal catalysts. In recent years, considerable attention has been paid to the carbonylation with non-precious metal catalysts under irradiation. In this dissertation, the effects of different non-precious metal catalysts, C1source and light source on the carbonylation of halohydrocarbon are investigated.The carbonylation of haloalkanes with CO catalyzed by non-precious metal catalysts was performed under irradiation of a high-pressure mercury lamp. The experimental results showed that with monobromoalkanes as substrates, CuCl2/(n-C4H9)3N was the most efficient catalyst among the tested catalysts, i.e. copper, tin, cadmium and cobalt compounds. In case of carbonylation of1-bromooctane, for example, methyl nonanoate was achieved with91%yield and91%selectivity. Furthermore, in case of straight-chain bromoalkanes, the ratio (≥95%) of the corresponding normal esters by copper, tin and cadmium catalyzed was obviously higher than that (≈80%) by cobalt catalyzed.As catalyzed by copper, the carbonylation of monochloroalkanes catalyzed by cadmium and cobalt compounds could proceed in the presence of iodide ion under irradiation. Among these catalytic systems, the cadmium compounds/iodides system exhibited the highest catalytic activity, e.g. the conversion of1-chlorooctane and the yield of methyl nonanoate were84%and68%in Cd(OAc)2/KI system, respectively. The MS analysis showed that the role of iodide ion was initially to form active iodoalkanes via substituting chloride ion in chloroalkanes in situ, and then, the carbonylation of iodoalkanes could proceed under irradiation.The carbonylation of dihaloalkanes with CO under irradiation was studied. With1,6-dibromohexane as substrate, the corresponding halogen ester Br(CH2)6CO2CH3was given, while the halogen ester Cl(CH2)6CO2CH3was obtained with1-bromo-6-chlorohexane and1,6-dichlorohexane as substrates. The yield and selectivity of Cl(CH2)6CO2CH3were as high as70%in the reaction of1-bromo-6-chlorohexane with CO catalyzed by CuBr2/(n-C4H9)3N.It was found that HCOOCH3could be utilized as a C1source in a convenient and safe way, and the carbonylation of haloalkanes catalyzed by non-precious metal catalysts could be completed in CH3OH-HCOOCH3without the use of external CO under irradiation, e.g. the yield and selectivity of methyl nonanoate from1-bromooctane and HCOOCH3were56%and62%, respectively. The mechanism of HCOOCH3participating in the carbonylation is verified by the IR analysis and the isotope experiment of CD3OD. The results suggested that HCOOCH3decomposed firstly into CO and CH3OH under irradiation, and the carbonylation of haloalkanes then proceeded. In addition, the results by ab initio quantum chemistry methods indicated that the process of HCOOCH3decomposing into CO and CH3OH was dynamically-favourable.With a254nm single wavelength lamp, the carbonylation of haloalkanes with CO catalyzed by non-precious metal catalysts could also be performed. However, no expected results were obtained, e.g. the conversion of1-bromooctane and the yield of methyl nonanoate were97%and62%in Co(OAc)2/NaOAc system, respectively.The carbonylation of bromobenzene and its derivatives with CO catalyzed by Co(OAc)2and CoCl2has also been investigated. The result indicated that the reaction could proceed not only under UV light but also under visible light in the presence of CH3ONa and PhCOPh. Under visible light, the yield and selectivity of methyl benzoate from bromobenzene were70%and100%when adding CH3ONa and PhCOPh to the Co(OAc)2catalytic system. The reactivities were greatly improved by chloro-substituent, the yields of the corresponding chloro-esters o,m,p-ClC6H4COOCH3were≥93%, while the activities of o, m, p-BrC6H4CH3were similar to bromobenzene.