The Research Of Copper Composite Catalyst Catalyzed Cleavage Reactions Of Carboxylic Esters In Nearly Neutral Conditions

Carboxylic esters are a kind of important compounds and the ester groups are often used as protection groups for hydroxyl groups. Recently, the synthesis of carboxylic esters has a broad research base. But its inverse process, the cleavage procedure of esters is relatively few. Therefore, the development of a mild and efficient method for the cleavage of esters as a deprotection procedure becomes a hot research topic in recent years.The cleavage research of carboxylic esters is applied in the acidic and alkaline conditions. But these conditions are not for the substrates which are sensitive to acid or alkali in the deprotection procedure. Therefore this dissertation focuses on the cleavage of esters in nearly neutral conditions. We found that sodium azide facilitated the cleavage of esters and copper (â…¡) played a considerable role in catalytic effect. Furthermore we found that basic cupric carbonate and sodium azide formed a new catalytic system, which could decompose carboxylic esters efficiently in nearly neutral conditions. And it was relatively efficient, cheap, selective and recyclable etc.The main content of this paper is to catalyze cleavage of the carboxylic esters in the methanol, with sodium azide and basic cupric carbonate as the catalysis in nearly neutral conditions. Firstly amyl acetate was selected as substrate in order to study optimized conditions, including catalysts, reaction time, reaction temperature, amount of sodium azide and amount of the metal catalyst. Then we synthesized a series of carboxylic esters and identified the structures by using infrared spectrometer. Finally, we decomposed these carboxylic esters in the optimized conditions, studied the decomposition law and investigated the reaction mechanism.The results indicated that the composite catalyst composed of basic cupric carbonate and sodium azide was efficient in the cleavage reactions of carboxylic esters. Most carboxylic esters had high decomposition rate and good selectivity. For the slow reaction in the selected conditions, we could improve the reaction temperature, increased the amount of catalyst or enhanced the solubility of sodium azide to make the reaction more complete. No elimination byproducts were formed. Moreover, we discovered that the cleavage reactions went more easily and the decomposition rate was higher if there was electron-drawing group in the carbonyl part or benzene ring in the alcohol part. In a word, the basic cupric carbonate and sodium azide are efficient to the reaction of the cleavage of carboxylic esters in nearly neutral conditions. Therefore, this paper establishes a catalytic cleavage system of carboxylic esters, which has such characteristics as mild reaction conditions, high efficiency and specificity etc. So it is a new method to decompose the carboxylic esters.