Synthesis of Strained Pyridine-Containing Cyclyne via Reductive Aromatization

The Sonogashira−Hagihara coupling reactions of 2,6-diiodopyridine and cis-3,6-diethynyl-3,6-dimethoxycyclohexa-1,4-diene or cis-9,10-diethynyl-9,10-dimethoxy-9,10-dihydroanthracene gave macrocyclic compounds having alternating 2,6-diethynylpyridine and 3,6-dimethoxycyclohexa-1,4-diene segments. Transformation of the C3-symmetric 2,6-diethynylpyridine-based cyclotrimer was efficiently achieved using tin-mediated reductive aromatization under mild conditions.