Tricyclo nonadiene

Barbaralane (Tricyclo[3.3.1.0 ]nonadiene) Degenerate Rearrangement and High Temperature Isomerizations 2.8.1 Substituted Barbaralanes... 

Pyrolysis of exo- and /2Jo-tricyclo[4.2.1.0 ]nonadiene gives bicyclo[4.2.1]nona-triene with log = 14.2 - 44230/2.37 r and log = 14.68 - 40 550/2.3/ r, respectively, presumably by a forbidden disrotatory ring opening in each case (Scheme 10.21). Of interest is the fact that the remote double bond has little effect on the rate since the 7,8-saturated materials have similar activation parameters. 

Thermal or photochemically induced rearrangement of the tricyclo[4,3,0,0 ]-nonadienes (496) gives the dihydroindenes (497). " The thermal stabilities of the tricyclic dienes is in the order d>c>e>b>a. This ordering is largely explicable on the basis of steric effects. 

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