Synthesis of unsymmetrical biaryl ureas from N-carbamoylimidazoles: kinetics and application
作者:Tristan Rawling、Andrew M. McDonagh、Bruce Tattam、Michael Murray
DOI:10.1016/j.tet.2012.05.002
日期:2012.7
N-Carbamoylimidazoles dissociate in solution to yield imidazole and an isocyanate that may be reacted with another aryl amine to form an unsymmetrical biaryl urea. This paper investigates the reaction kinetics and the influence of electron withdrawing/donating substituents on the reaction of N-carbamoylimidazoles with aniline. The overall reaction mechanism involves two zwitterionic intermediates,
N-氨基咪唑在溶液中解离,生成咪唑和异氰酸酯,该异氰酸酯可与另一种芳基胺反应形成不对称的联芳基脲。本文研究了反应动力学以及吸电子/给电子取代基对氮反应的影响-氨基甲酰咪唑与苯胺。整个反应机理涉及两个两性离子中间体,它们在离解过程中以及释放的异氰酸酯与苯胺反应时形成。该反应的限速步骤是来自第二两性离子中间体的碱催化的质子转移。尽管芳基上的吸电子取代基阻碍了解离,但与带有给电子取代基的化合物相比,它们显着提高了反应速率。解离时释放的咪唑催化速率确定步骤,因此解离的N-氨基甲酰咪唑的反应比仅涉及异氰酸酯的反应进行得更快。另外,咪唑消除了对无水反应条件的需要。该ñ制备索拉非尼(一种联芳基脲激酶抑制剂)以高收率和优异的纯度证明了-氨基甲酰咪唑的方法学。