Yasutomo Segawa, Takuya Kuwabara, Katsuma Matsui, Satoru Kawai, and Kenichiro Itami
Tetrahedron (Special Issue), 2015, ASAP, DOI: 10.1016/j.tet.2015.02.066
A palladium-free, short-step synthesis of cycloparaphenylene (CPP) has been developed. The key macrocyclization step was performed by a nickel-mediated homocoupling of a newly designed U-shaped unit. Surprisingly, the rectangular macrocycle was obtained in high yield compared with previous macrocyclization reactions in CPP syntheses. X-ray crystallography as well as DFT calculation revealed unstrained structure of the macrocycle.