钯催化 1,3-丁二烯羧酯化合成 3-戊烯酸甲酯

 以 1,3-丁二烯、CO 和甲醇为原料, 进行羧酯化反应合成 3-戊烯酸甲酯是 Altam 路线生产己内酰胺绿色工艺的关键步骤. 将 Pd 与三齿 N-杂环配体或双膦配体组成的催化体系用于 1,3-丁二烯的羧酯化反应中, 其中乙酸钯/2,6-二 (3,5-二甲基吡唑基) 吡啶催化剂表现出中等的催化活性, 在 150 ºC, p(CO) = 6.0 MPa 的优化条件下反应 6 h, 1,3-丁二烯转化率为 78.8%, 3-戊烯酸甲酯选择性达 92.2% (TON = 226); 而乙酸钯/2,2?-二 (二苯基膦基) 苯醚催化体系的活性更高, 在优化反应条件下, 1,3-丁二烯转化率达 90.4%, 3-戊烯酸甲酯选择性为 91.6% (TON = 181). 在 200 ºC 及类似的羧酯化反应条件下, 1,3-丁二烯发生二聚反应, 其转化率为 99% 以上, 二聚产物 4-乙烯基-1-环己烯选择性高于 96%.

Palladium Catalyzed Carboxylation of 1,3-Butadiene to Methyl 3-Pentenoate

Palladium salts with N-heterocyclic ligand or biphosphine ligand were used as the catalysts for the carboxylation of 1,3-butadiene with carbon monoxide in methanol to methyl 3-pentenoate, which is one of the key reactions in Altam process for production of ?-caprolactam. The combination of Pd(OAc)2 with 2,6-bis(3,5-dimethylpyrazol-1-yl)pyridine exhibited moderate catalytic activity under the optimized conditions (150 ºC, p(CO) = 6.0 MPa, 6 h), reaching 78.8% conversion of 1,3-butadiene and 92.2% selectivity for the target product (TON = 226). Using Pd(OAc)2/(oxydi-2,1-phenylene)bis(diphenylphosphine) as the catalyst remarkably increased the reaction efficiency, achieving 90.4% conversion of 1,3-butadiene and 91.6% selectivity for the product (TON = 181). At temperature above 200 ºC, 1,3-butadiene underwent dimerization to form 4-vinyl-1-cyclohexene in 96% yield.