Phenanthrenes are polycyclic aromatic hydrocarbons (PAHs) composed of three fused benzene rings. These structural units are found, e.g., in pharmaceutical chemistry or materials chemistry. Approaches to the synthesis of this type of compound are interesting research targets.

Xiaoming Zeng, Sichuan University, Chengdu, China, and colleagues have developed a chromium-catalyzed reaction using an inexpensive CrCl₂ salt and allylmagnesium bromide for promoting the functionalization of unactivated C–H bonds of E/Z-mixed 1-halo-2-styrylarenes. The reactions were performed in a mixture of diethyl ether (Et₂O) and tetrahydrofuran (THF) at room temperature within 4 h.

Under these conditions, the team achieved an intramolecular coupling between the C–H bonds and the C–halide bonds on the scene. Overall, the work provides a method for the preparation of functionalized phenanthrene derivatives under mild conditions.

• Cr-Catalyzed Intramolecular Arylative Cross-Coupling of Unactivated C–H Bonds with C–Halide Bonds,
  Xuelan Wang, Jiaoyue Zhong, Meiming Luo, Xiaoming Zeng,
  Org. Lett. 2024.
  https://doi.org/10.1021/acs.orglett.4c01145