The discoveries of new forms of carbon have always opened doors to new science and technology. In 1991, three-dimensional (3D) periodic carbon crystals with negative Gaussian curvatures that consist of six- and eight-membered rings were proposed. To realize these 3D periodic carbon crystals (known as Mackay crystals), methods for creating polyaromatic structures embedding eight-membered rings must be developed. Here we report two annulative coupling reactions that form an eight-membered ring through catalytic C–H functionalization. We have discovered that bay-chlorinated polyaromatics undergo either annulative dimerization or cross-coupling with biphenylene in the presence of a palladium catalyst to form various hitherto inaccessible polyaromatics embedding an eight-membered ring. The threefold annulative cross-coupling of 1,5,9-trichlorotriphenylene allowed construction of a highly curved nanocarbon. The present work not only demonstrates the potential of annulative coupling for constructing octagonal nanocarbons but also provides a conceptual pathway for the synthetic realization of 3D periodic carbon crystals.

新形式碳的发现一直为新科学和技术打开大门。1991年，提出了由六元和八元环组成的具有负高斯曲率的三维（3D）周期性碳晶体。为了实现这些3D周期性碳晶体（称为Mackay晶体），必须开发出创建嵌入八元环的多芳族结构的方法。在这里，我们报告了两个环状偶联反应，它们通过催化C–H官能化形成一个八元环。我们发现了那个海湾氯化聚芳族化合物在钯催化剂的存在下进行环二聚或与联苯交叉偶联，形成嵌入八元环的各种迄今难以接近的聚芳族化合物。1,5,9-三氯三亚苯基的三重环形交叉偶联可构建高度弯曲的纳米碳。本工作不仅证明了环状八方纳米碳的环状偶联的潜力，而且为3D周期碳晶体的合成实现提供了概念途径。