Noriceane (Tetracyclo2,6.04,9>undecane) and 3,5-Dehydronoriceane (Pentacyclo2,6.03,5.04,9>undecane)

Article abstract of DOI:10.1246/bcsj.55.3245

Heating a mixture of endo, exo- and endo, endo-2,4-dibromohomoadamantanes at 180 deg C in hexamethylphosphoric triamide (HMPT) brings about a novel skeletal rearrangement with concomitant dehydrobromination to give tricyclo<5.3.1.0^4,9>undeca-2,5-diene (5) in 88percent yield.Direct photoexcitation of 5 in diethyl ether induces an intramolecular <2+2> cycloaddition to produce 3,5-dehydronoriceane (2).The bicyclo<2.1.0>pentane moiety constrained in the cage structure of 2 shows almost the same 13C-H coupling constants as those of bicyclo<2.1.0>pentane itself.Finally hydrogenation of 2 over PtO2 easily proceeds to afford noriceane, which is named after the structure of iceane.