Studies On Cobalt Or Palladium Catalysts For The Carbonylation Of Organic Halides

Transition metal catalyzed carbonylation reaction of organic halides represents one of the most powerful methods for the synthesis of a diverse array of carboxylic acids and their derivatives, which has become an important and attractive direction of C1chemistry because of its flexibility and versatility with regard to easy available substrates, good functional group tolerance, high atom-economy, and high efficiency. Because of the great significance of these reactions, they were widely used in the chemical industry for the synthesis of bulk chemicals, fine chemicals, special chemicals, and polymers. However, some carbonylation reactions that have great potential for industrial applications, have suffered from either harsh reaction conditions, or low efficiency. Moreover, most applications for the carbonylation reactions of organic halides involve homogeneous catalysts. These homogeneous catalytic systems generally exhibit good activity and selectivity, but they suffer from the practical problems such as catalyst separation and recycling. Hence, enhancing the existing catalytic system and searching more efficient catalytic reaction from homogeneous to heterogeneous system, will promote the industrialization process of some carbonylation reactions.In this dissertation, we studied cobalt or palladium-catalyzed carbonylation reactions of organic halides from the three aspects:searching new catalytic reaction systems, enhancing the existing catalytic synthesis system, and exploring new heterogeneous catalytic system. It mainly consists of the following six parts:Chapter1. A brief introduction of carbonylation reaction was first given, and then the development of cobalt and palladium catalyzed carbonylation of organic halides for the synthesis of carboxylic acid esters, amides, and aryl carboxylic acids, was surveyed in detail. The reaction mechanisms for palladium and cobalt-catalyzed carbonylation of organic halides were also briefly summarized.Chapter2. Carbonylation of quaternary ammonium salts was investigated. Tertiary amides could be obtained via carbonylation of quaternary ammonium halides using cobalt complex as the catalyst, the yields of some amides were around or above95%. Furthermore, the main byproduct alkyl halides produced in the reaction could be easily recovered and reused as the raw materials for the synthesis of quaternary ammonium halides. By means of designing experiment, it was found that C-N bonds in quaternary ammonium salts could be cleaved by thermal decomposition and catalytic effect, the reaction mechanism was also discussed in detail. This work presents a new and efficient approach for synthesizing some tertiary amides, and it is also meaningful for recognizing the stability of quaternary ammonium salts where they are used as solvents or promoters in catalytic carbonylation reactions.Chapter3. To develop a more active catalytic system for the synthesis of tertiary amides, we investigated palladium-catalyzed carbonylation of quaternary ammonium halides. The influences of various parameters were investigated. It was found that ligand-free PdCl2showed efficient catalytic performance for this transformation, a palladium catalyst loading as low as0.05mol%was sufficient for moderate to high yield (76.9-96.9%) of tertiary amides, and the highest TOF could be up to289h"1. Under optimum conditions, the catalytic activity of commercial palladium on activated carbon (Pd/C) catalyst was also evaluated. The Pd/C catalyst exhibited high catalytic activity for this carbonylation reaction and could be recycled well. This process can be a great potential procedure for the preparation of certain tertiary amides in industry.Chapter4. Carbonylation of organic chlorides for the preparation of carboxylic acid esters was investigated. The influences of various parameters were investigated using the ethoxycarbonylation of CH2CI2as a model reaction. Ligand-free PdCl2with the aid of Bu4NI showed efficient catalytic performance for this hard transformation. Under optimal conditions, the total yield of esters could be up to67.3%. The scope of the catalyst is relatively broad, several kinds of organic chlorides can be carbonylated to corresponding esters in moderate to excellent yields. Moreover, the effect of Bu4NI on the reaction was discussed in detail and it was critical in both stabilizing the ligand free Pd catalytic system and activating the inert C-Cl bond in the reaction. Based on the experimental results, a possible reaction model of PdCl2/Bu4NI catalytic carbonylation system was proposed.Chapter5. Porous organic polymers (POPs), emerged just in a few years ago, have great potential applications in heterogeneous catalysis due to their unique properties such as large surface area, low skeletal density, high chemical stability, and the ability to introduce a broad range of useful chemical functionalities into the porous frameworks. In this chapter, alkoxycarbonylation of aryl halides using a palladium supported on triphenylphosphine-functionalized microporous polymer catalyst was investigated. This catalyst showed high catalytic activity for the alkoxycarbonylation of aryl iodides. Under balloon pressure of CO, various aryl iodides on carbonylation with alcohols and phenols gave the corresponding products in moderate to excellent yields (74-99%). The catalyst can be recycled at least ten times without significant loss of its catalytic activity, and the Pd leaching from the porous organic polymers is quite low.Chapter6. Water is a cheap, safe, and nontoxic solvent in reactions and has thus attracted considerable attention when it is used as a solvent in the organic synthesis. Generally, the carbonylation reactions in water require water-soluble homogeneous catalysts, but they suffer from the practical problems such as catalyst separation and recycling. In this chapter, an amphiphilic and porous polyurea was prepared by a facile urea-forming condensation reaction. The porous polyurea was used as an effective support for palladium-catalyzed hydroxycarbonylation reaction of aryl iodides in water, excellent catalytic activity and good reusability were observed. Based on the results, the relationship between structural and catalytic properties of the catalyst was investigated. It was found that the superior catalytic performance was mainly attributed to good amphipathicity of urea-based porous polymer. This study opens a new avenue to developing heterogeneous catalytic systems for carbonylation reactions in water medium.