108148-32-9Relevant articles and documents
The Pagodane Route to Dodecahedranes Directed Conversions - The Pagodane -> Bissecododecahedradiene Stage
Fessner, Wolf-Dieter,Murty, Bulusu A. R. C.,Spurr, Paul R.,Pinkos, Rolf,Melder, Johann-Peter,et al.
, p. 1697 - 1718 (2007/10/02)
Three conceptual routes (A, B, C) from pagodane (1) to pentagonal dodecahedrane (2) are evaluated by MM2 (MM3) calculations.After limited experimental success with a catalytic one-pot route (A), a more selective transformation along one of two stepwise routes (B/C) is explored.An expeditious entry into route C is achieved by hydrogenolytic cyclobutane opening in 1; secopagodane 7 (100percent), however, resists both progression along route C (dehydrogenative C-C bond formation to isododecahedrane 8) and crossover into routes B (hydrogenolysis to bissecododecahedrane 5).The first transformation along route B, the 2? -> 2?- isomerization of the highly strained 1 to bissedodecahedra-1,10(11)-diene 3, is not attainable by metal catalysis and cannot productively brought about by thermal activation: The necessarily very high reaction temperatures (>700 deg C) enforce instead a mechanistically interesting fragmentation into two C10H10 halves to give ultimately naphthalene.The very rapid pagodane opening occuring after one-electron oxidation, too, is not a preparatively useful alternative.Highly efficient, on the other hand, is a two-step process affording a high yield of the product and consisting of regiospecific, photochemically induced bromine addition to the central four-membered ring (-> dibromosecopagodane 37) followed by reductive bromine elimination (-> diene 3).In spite of the necessarily rather severe reaction conditions in both steps, this procedure is applicable to the preparation of various 3,8-difunctionalized bissecodienes (dienedione 11, diene diesters 43, 50, 52, dichlorodiene 56).Limitations of this procedure are met with the 4,4,9,9-tetrachloropagodane 60 (inert) and the pagodane 80 (bridge-head bromination).The lateral half-cages of the (seco)-pagodane structures are explored for preparatively (dis)advantageous steric effects, that might be later exploited on the way towards functionalized dodecahedrane derivatives. Key Words: Pagodane -> dodecahedrane pathways / Pagodane opening reactions / Cage effects
