Johns Adam M, Utsunomiya Masaru, Incarvito Christopher D, Hartwig John F
Department of Chemistry, Yale University, P.O. Box 208107, New Haven, CT 06520-8107, USA.
J Am Chem Soc. 2006 Feb 15;128(6):1828-39. doi: 10.1021/ja056003z.
We report a catalyst for intermolecular hydroamination of vinylarenes that is substantially more active for this process than catalysts published previously. With this more reactive catalyst, we demonstrate that additions of amines to vinylarenes and dienes occur in the presence of potentially reactive functional groups, such as ketones with enolizable hydrogens, free alcohols, free carboxylic acids, free amides, nitriles, and esters. The catalyst for these reactions is generated from Pd(eta(3)-allyl)Cl (with or without added AgOTf) or Pd(CH(3)CN)(4)(2) and Xantphos (9,9-dimethyl-4,5-bis(diphenylphosphino)xanthene), which generates complexes with large P-Pd-P bite angles. Studies on the rate of the C-N bond-forming step that occurs by attack of amine on an eta(3)-phenethyl and an eta(3)-allyl complex were conducted to determine the effect of the bite angle on the rate of this nucleophilic attack. Studies on model eta(3)-benzyl complexes containing various bisphosphines showed that the nucleophilic attack was faster for complexes containing larger P-Pd-P bite angles. Studies of substituted unsymmetrical and unsubstituted symmetrical model eta(3)-allyl complexes showed that nucleophilic attack on complexes ligated by Xantphos was faster than on complexes bearing ligands with smaller bite angles and that nucleophilic attack on unsymmetrical allyl complexes with larger bite angle ligands was faster than on unsymmetrical allyl complexes with smaller bite angle ligands. However, monitoring of catalytic reactions of dienes by (31)P NMR spectroscopy showed that the concentration of active catalyst was the major factor that controlled rates for reactions of symmetrical dienes catalyzed by complexes of phosphines with smaller bite angles. The identity of the counterion also affected the rate of attack: reactions of allylpalladium complexes with chloride counterion occurred faster than reactions of allylpalladium complexes with triflate or tetrafluoroborate counterion. As is often observed, the dynamics of the allyl and benzyl complexes also depended on the identity of the counterion.
我们报道了一种用于乙烯基芳烃分子间氢胺化反应的催化剂，该催化剂在此反应过程中的活性远高于此前报道的催化剂。使用这种活性更高的催化剂，我们证明了在存在潜在反应性官能团（如带有可烯醇化氢的酮、游离醇、游离羧酸、游离酰胺、腈和酯）的情况下，胺能够加成到乙烯基芳烃和二烯烃上。这些反应的催化剂由[Pd(η(3)-烯丙基)Cl]₂（添加或不添加AgOTf）或Pd(CH₃CN)₄₂与Xantphos（9,9-二甲基-4,5-双（二苯基膦基）呫吨）生成，它们形成具有较大P-Pd-P咬角的配合物。通过胺进攻η(3)-苯乙基和η(3)-烯丙基配合物发生的C-N键形成步骤的速率研究，以确定咬角对这种亲核进攻速率的影响。对含有各种双膦的模型η(3)-苄基配合物的研究表明，对于含有较大P-Pd-P咬角的配合物，亲核进攻更快。对取代的不对称和未取代的对称模型η(3)-烯丙基配合物的研究表明，对由Xantphos配位的配合物的亲核进攻比对具有较小咬角配体的配合物更快，并且对具有较大咬角配体的不对称烯丙基配合物的亲核进攻比对具有较小咬角配体的不对称烯丙基配合物更快。然而，通过³¹P NMR光谱监测二烯烃的催化反应表明，活性催化剂的浓度是控制由具有较小咬角的膦配合物催化的对称二烯烃反应速率的主要因素。抗衡离子的身份也影响进攻速率：烯丙基钯配合物与氯离子抗衡离子的反应比烯丙基钯配合物与三氟甲磺酸根或四氟硼酸根抗衡离子的反应更快。正如经常观察到的那样，烯丙基和苄基配合物的动力学也取决于抗衡离子的身份。
