5773-47-7Relevant articles and documents
The C8H12-Energy Hypersurface Thermolysis of syn- and anti-Tricyclo2,5>octane. Experimental and Theoretical Studies
Martin, Hans-Dieter,Eisenmann, Erwin,Kunze, Michael,Bonacic-Koutecky, Vlasta
, p. 1153 - 1179 (2007/10/02)
The thermal behaviour of syn- and anti-tricyclo2,5>octanes 9 and 10 in the gas phase as well as in solution is investigated.Two main products are formed in parallel reactions: cis,cis-1,5-cyclooctadiene (11) and cis,trans-1,5-cyclooctadiene (15), the latter being partly isomerized to 11 under the reaction conditions.Minor products are cis-1,2-divinylcyclobutane (6), trans-1,2-divinylcyclobutane (16) and 4-vinyl-1-cyclohexene (17).Thermolysis of cis-1,2-divinylcyclobutane leads to small amounts of cis,trans-cyclooctadiene, presumably via a four-centre transition state.The tricyclics most likely prefer a stepwise isomerization.The decisive product-controlling factor seems to be the conformational mobility of intermediate diradicals.By comparison with the boat-Cope reaction of divinylcyclobutane the pericyclic six-centre transition state of this rearrangements is shown to lie energetically about 19 kcal/mol below the transition states in the thermolysis of 9 and 10.The azo compound 12 on heating fragments predominantly in a concerted manner in contrast to the photolysis.Theoretical methods are applied to unveil structure and bonding in the supposed intermediate diradicals.
