Mg. Banwell et Jh. Ryan, SYNTHESIS AND SPECTROSCOPIC CHARACTERIZATION OF 4-CHLORO-[6](3,5)-TROPONOPHANE, Journal of the Chemical Society, Chemical Communications, (13), 1994, pp. 1603-1604
Treatment of the tricyclic enone 4d with perchloric acid results in th
e formation of the title troponophane 3d which contains the shortest (
3,5)-polymethylene bridge reported to date.