Ali Yahia, Chen Liao, Levin Mark D
Department of Chemistry, University of Chicago, 5735 S Ellis Avenue, Chicago, IL 60637 (USA).
Tetrahedron Lett. 2025 Aug 30;167. doi: 10.1016/j.tetlet.2025.155684. Epub 2025 May 29.
Atom insertion reactions into ring systems may occur via one of two pathways, proceeding either through initial cyclization to form a 3-membered ring intermediate followed by cleavage of the ring-fusion bond, or through initial ring-scission followed by recyclization onto the inserting atom. Herein, we demonstrate the use of regioretention probes, substrates with latent symmetry that is unveiled only in the case of ring scission and are thus able to distinguish between possible mechanisms for atom insertion. We apply these probes to a handful of previously reported nitrogen insertion methods and in each case unambiguously establish whether the reaction proceeds through aziridination or C=C cleavage. In particular, we show that recently reported cobalt- or manganese-catalyzed nitrogen insertion protocols, postulated to proceed via an aziridinyl radical intermediate, instead proceed through a ring-opened ketone-containing intermediate.
原子插入环状体系的反应可能通过两种途径之一发生，要么先进行环化形成三元环中间体，然后断裂环融合键，要么先进行开环，然后再环化到插入原子上。在此，我们展示了区域保留探针的应用，这些底物具有潜在对称性，只有在开环情况下才会显现，因此能够区分原子插入的可能机制。我们将这些探针应用于一些先前报道的氮插入方法，在每种情况下都明确确定反应是通过氮杂环丙烷化还是碳碳双键断裂进行。特别是，我们表明最近报道的钴或锰催化的氮插入方案，推测是通过氮杂环丙基自由基中间体进行的，实际上是通过含开环酮的中间体进行的。
