The Pagodane Route to Dodecahedranes Unsaturated (Hyperstable) and Saturated Bissecododecahedranes

In bissecododecahedra‐1,10(11)‐dienes, the syn ‐periplanar and unusually proximate arrangement of the π bonds is responsible for extraordinary physical properties such as strong throughspace homoconjugation, low oxidation potentials, and a special reactivity pattern. In pursuit of route B to dodecahedranes [1] , the hyperstability predicted (MM2) for these bissecodienes and the related monoenes has been experimentally verified only for the latter in their resistance towards catalytic hydrogenation. Non‐hydrogenative saturation of (3,8‐difunctionalized) bissecodienes ( 3, 8, 13 ) and monoenes ( 4, 9, 14 ) becomes increasingly hampered due to the increased steric congestion on the more spherical molecular surfaces but can be achieved in „high‐driving‐force” reactions [ cis ‐hydroxylation ( 26, 27, 41, 42 ), epoxidation ( 38, 54, 57, 58, 60, 63, 80, 83 ), cyclopropanation ( 55, 59, 61, 64 ]. In contrast, cycloadditive four‐, five‐ ( 73 ), and six‐membered ( 76 ) ring annulation again is limited to monoadditions. The half‐cages in the bissecododecahedrane structures provide for remarkable steric steering and protection [e.g. anti ‐selective protonation (alkylation) of carbanions 57a ( 84a ) 2‐ , lack of hydrazone formation from ketones 58, 89 , resistance of syn ‐bis(acid chloride) 86 towards hydrolysis.