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通过密度泛函方法(DFT)研究了零价钯和苯甲酸共催化内炔烃氢胺化反应的机理.计算研究表明,文献中推测的通过苯甲酸的O—H键氧化加成到零价钯上形成钯氢中间体并不是启动该反应的有利途径.机理如下:在零价钯炔烃复合物上,苯甲酸可以通过质子转移到炔烃的途径得到二价烯基钯中间体,生成的羧酸根阴离子可以进一步辅助底物发生β-氢消除反应生成联烯中间体,随后在零价钯联烯复合物上,再次通过苯甲酸质子转移得到烯丙基钯中间体,最后胺亲核进攻烯丙基末端碳得到最终氢胺化产物.
The mechanism of cocatalytic hydrogenation of internal alkynes by zero-valent palladium and benzoic acid was studied by density functional theory (DFT). The calculations show that the oxidation of O-H bond by benzoic acid to zero valence The formation of palladium on hydrogen palladium hydrogen intermediate is not an advantageous way to start the reaction mechanism is as follows: In the zero-valent palladium alkyne complex, benzoic acid can be transferred to the alkyne by proton to get bivalent alkenyl palladium intermediates to generate Of the carboxylate anion can further assist the substrate β-hydrogen elimination reaction generated ene intermediates, and then in the zero-valent palladium ene complex, again through the proton transfer of benzoic acid to give allyl palladium intermediate, the final amine nucleophilic The attack on allyl-terminated carbon gives the final hydrogenation product.