Departamento de Química Orgánica, Facultad de Química, and ‡Sección Universitaria de Instrumentación Científica, Servicio de Apoyo a la Investigación, Regional Campus of International Excellence "Campus Mare Nostrum", Universidad de Murcia , E-30100 Murcia, Spain.
J Am Chem Soc. 2016 Jul 20;138(28):8726-9. doi: 10.1021/jacs.6b05581. Epub 2016 Jul 6.
The intramolecular cyclization of N-benzylfumaramide [2]rotaxanes is described. The mechanical bond of these substrates activates this transformation to proceed in high yields and in a regio- and diastereoselective manner, giving interlocked 3,4-disubstituted trans-azetidin-2-ones. This activation effect markedly differs from the more common shielding protection of threaded functions by the macrocycle, in this case promoting an unusual and disfavored 4-exo-trig ring closure. Kinetic and synthetic studies allowed us to delineate an advantageous approach toward β-lactams based on a two-step, one-pot protocol: an intramolecular ring closure followed by a thermally induced dethreading step. The advantages of carrying out this cyclization in the confined space of a benzylic amide macrocycle are attributed to its anchimeric assistance.
描述了 N-苄基富马酰胺[2]轮烷的分子内环化反应。这些底物的机械键激活了这种转化，以高产率和区域选择性及立体选择性的方式进行，得到了互锁的 3,4-二取代反式氮杂环丁-2-酮。这种激活效应与更常见的通过大环屏蔽保护线程功能明显不同，在这种情况下促进了不寻常和不利的 4-外消旋-三键环闭合。动力学和合成研究使我们能够描绘出一种基于两步一锅法的基于β-内酰胺的有利方法：分子内环化反应，然后是热诱导的脱螺纹步骤。在苄基酰胺大环的受限空间中进行这种环化反应的优势归因于其邻助作用。
