The development of innovative strategies for the synthesis of N-heterocyclic compounds is an important topic in organic synthesis. Ring expansion methods to form large N-heterocycles often involve the cycloaddition of strained aza rings with π bonds. However, in some cases such strategies suffer from some limitations owing to the difficulties in controlling the regioselectivity and the accessibility of specific π-bond synthons. Here, we report the development of a general ring expansion strategy that involves a formal cross-dimerization between three-membered aza heterocycles and three- and four-membered-ring ketones through synergistic bimetallic catalysis. These formal cross-dimerizations of two different strained rings are efficient and scalable, and provide a straightforward and broadly applicable means of assembling diverse N-heterocycles, such as 3-benzazepinones, dihydropyridinones and uracils, which are versatile units in numerous drugs and biologically active compounds. Preliminary mechanistic studies revealed that the C–C bond of strained ring ketones is first cleaved by the Pd⁰ species during the reaction.

开发合成 N-杂环化合物的创新策略是有机合成中的一个重要课题。形成大 N-杂环的环扩展方法通常涉及具有 π 键的应变氮杂环的环加成。然而，在某些情况下，由于难以控制区域选择性和特定 π 键合成子的可及性，此类策略会受到一些限制。在这里，我们报告了一种通用扩环策略的发展，该策略涉及通过协同双金属催化在三元氮杂杂环与三元环和四元环酮之间进行正式的交叉二聚化。两个不同应变环的这些正式交叉二聚化是高效且可扩展的，并提供了一种直接且广泛适用的组装不同 N-杂环的方法，例如 3-苯并氮杂酮、二氢吡啶酮和尿嘧啶，它们是许多药物和生物活性化合物中的多功能单元。初步的机理研究表明，应变环酮的 C-C 键首先被 Pd 裂解⁰种在反应过程中。