Calafat Sofía Varela, Durantini Edgardo N, Chiacchiera Stella M, Silber Juana J
Departamento de Química, Universidad Nacional de Río Cuarto, Agencia Postal # 3, Río Cuarto X5804BYA, Argentina.
J Org Chem. 2005 Jun 10;70(12):4659-66. doi: 10.1021/jo0483320.
Phase-transfer catalysis (PTC) is a widely accepted methodology in organic synthesis. Although a great number of organic syntheses were reported in PTC conditions, systematic kinetic studies are scarce. In the present report, a detailed study of the kinetics of the reaction between 2-chloro-5-nitrotrifluoromethylbenzene (CNTFB) and 2-phenylpropionitrile anion (HPP-), under PTC, was performed under several conditions. The reaction was carried out either in toluene or chlorobenzene as the organic phase, in the presence of a concentrated aqueous solution of NaOH using tetraalkylammonium (Q+X-) salts as phase-transfer catalysts. The major product was 2-(4-nitro-2-trifluoromethylphenyl)-2-phenylpropionitrile, and its yield depends on the experimental conditions. Different aspects of the mechanism are discussed and quantified. Kinetic data were explained by means of an interfacial mechanism that involves the deprotonation of the adsorbed nucleophile precursor followed by its catalyst-mediated extraction to the organic phase. A multicomponent Langmuir-type interface was assumed. Although the extraction of OH- by catalyst to the organic phase is usually disregarded, the formation of the substrate hydrolysis product that leads to catalyst poisoning was also investigated. The influence of this side reaction on the yield of the main product was established. A discussion about the influence of this side process on the main reaction and the operating mechanism is presented.
相转移催化（PTC）是有机合成中一种广泛接受的方法。尽管在PTC条件下报道了大量有机合成反应，但系统的动力学研究却很少。在本报告中，在几种条件下对2-氯-5-硝基三氟甲基苯（CNTFB）与2-苯基丙腈阴离子（HPP-）在PTC条件下的反应动力学进行了详细研究。该反应在甲苯或氯苯作为有机相的情况下进行，在浓氢氧化钠水溶液存在下，使用四烷基铵（Q+X-）盐作为相转移催化剂。主要产物是2-（4-硝基-2-三氟甲基苯基）-2-苯基丙腈，其产率取决于实验条件。对反应机理的不同方面进行了讨论和量化。动力学数据通过一种界面机理进行解释，该机理涉及吸附的亲核前体的去质子化，随后其通过催化剂介导萃取到有机相中。假定存在多组分朗缪尔型界面。尽管通常忽略催化剂将OH-萃取到有机相的过程，但也研究了导致催化剂中毒的底物水解产物的形成。确定了该副反应对主要产物产率的影响。对该副反应对主反应的影响及操作机理进行了讨论。
