Department of Chemistry , University of California , Berkeley , California 94720 , United States.
Chemical Sciences Division , Lawrence Berkeley National Laboratory , 1 Cyclotron Road , Berkeley , California 94720 , United States.
J Am Chem Soc. 2018 Jun 27;140(25):7979-7993. doi: 10.1021/jacs.8b04073. Epub 2018 Jun 18.
Mechanistic information on a reliable, palladium-catalyzed aminocarbonylation of aryl chlorides with ammonia is reported. The reaction occurs with ethylene complex 1 as catalyst, and mechanistic information was gained by isolation of catalytic intermediates and kinetic measurements, including the first mechanistic data on the oxidative addition of aryl chloride to a palladium(0) complex in the presence of CO. Arylpalladium and phenacylpalladium halide intermediates were synthesized, and kinetic measurements of the formation and reactions of these intermediates were undertaken to determine the mechanism of the oxidative addition of aryl bromides and chlorides to a Pd(0) dicarbonyl compound in the presence of CO and the mechanism of the reaction of ammonia with a Pd(II) phenacyl complex to form benzamide. The oxidative addition of aryl chlorides and aryl bromides was determined to occur with rate-limiting reaction of the haloarene with a three-coordinate Pd(0) species bearing a bidentate phosphine and one CO ligand. A primary C kinetic isotope effect suggested that this step involves cleavage of the carbon-halogen bond. Our data show that the formation of benzamide from the reaction of phenacylpalladium halide complexes with ammonia occurs by a pathway involving reversible displacement of chloride from a phenacylpalladium chloride complex by ammonia, deprotonation of the bound ammonia to form a phenacylpalladium amido complex, and reductive elimination to form the C-N bond. Consistent with this mechanism, the reaction of an aryl palladium amido complex with CO formed the corresponding primary benzamide. A catalyst deactivation pathway involving the formation of a Pd(I) dimer also was elucidated.
报道了一种可靠的、钯催化的芳基氯化物与氨的氨基甲酰化反应的机理信息。该反应以乙烯配合物 1 为催化剂进行，通过分离催化中间体和动力学测量获得了机理信息，包括在 CO 存在下芳基氯化物与钯(0)配合物的氧化加成的第一个机理数据。合成了芳基钯和苯乙酮钯卤化物中间体，并对这些中间体的形成和反应进行了动力学测量，以确定在 CO 存在下芳基溴化物和氯化物与 Pd(0)二羰基化合物的氧化加成反应的机理以及氨与 Pd(II)苯乙酮配合物反应形成苯甲酰胺的机理。芳基氯化物和芳基溴化物的氧化加成被确定为卤代芳烃与具有双齿膦和一个 CO 配体的三配位 Pd(0)物种的限速反应。初步的 C 动力学同位素效应表明，这一步涉及碳-卤键的断裂。我们的数据表明，从苯乙酮钯卤化物配合物与氨的反应形成苯甲酰胺的反应途径涉及氨可逆取代苯乙酮钯氯配合物中的氯，形成苯乙酮钯酰胺配合物的结合氨去质子化，以及形成 C-N 键的还原消除。与该机理一致，芳基钯酰胺配合物与 CO 的反应形成相应的伯苯甲酰胺。还阐明了一种涉及 Pd(I)二聚体形成的催化剂失活途径。
