Catalytic Cage Formation via Controlled Dimerization of Norbornadienes: An Entry to Functionalized HCTDs (Heptacyclo­[6.6.0.02,6.03,13.04,11.05,9.010,14]­tetradecanes)

A general and practical catalytic method has been developed for the rapid synthesis of HCTD (heptacyclo­[6.6.0.02,6.03,13.04,11.05,9.010,14]­tetradecanes) and various new 7,12-disubstituted HCTDs from norbornadienes. Compared to the known approaches, this new protocol avoids stoichiometric metals, utilizes commercially available reagents as catalysts, and affords higher yields and significantly improved selectivity. In addition, quadracyclane was discovered for the first time to undergo a similar endo,cis,endo cycloaddition to give HCTD in a good yield. Derivatization of HCTDs led to efficient preparation of a range of novel homo- and heterobifunctional scaffolds that hold potentials for biological and material applications.