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The Pagodane Route to Dodecahedranes Directed Conversions – The Pagodane → Bissecododecahedradiene Stage
Author(s) -
Fessner WolfDieter,
Murty Bulusu A. R. C.,
Spurr Paul R.,
Pinkos Rolf,
Melder JohannPeter,
Fritz Hans,
Prinzbach Horst
Publication year - 1992
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19921250727
Subject(s) - chemistry , isomerization , hydrogenolysis , diene , yield (engineering) , bromine , catalysis , stereochemistry , aromatization , cyclobutane , naphthalene , cycloheptene , ring (chemistry) , medicinal chemistry , combinatorial chemistry , organic chemistry , natural rubber , materials science , metallurgy
Three conceptual routes (A, B, C) from [1.1.1.1]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 (100%), however, resists both progression along route C (dehydrogenative C—C bond formation to isododecahedrane 8 ) and crossover into route B (hydrogenolysis to bissecododecahedrane 5 ). The first transformation along route B, the 2sigma;→2π‐isomerization of the highly strained 1 to bissedodecahedra‐1,10(11)‐diene 3 , is not attainable by metal catalysis and cannot productively be brought about by thermal activation: The necessarily very high reaction temperatures (> 700°C) enforce instead a mechanistically interesting fragmentation into two C 10 H 10 halves to give ultimately naphthalene. The very rapid pagodane opening occurring 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 [2.2.1.1]pagodane 80 (bridgehead 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.