1.2- benzo-1.3-cycloheptadiene

It is perhaps worth pointing out that the di-i -methane rearrangements of 1,4-cycloheptadienes produce bicyclo[4.1.0]alkenes which are present in several natural products (e.g. in carenes). However, the most striking utility is perhaps evident in polycyclic transformations. The di-rr-methane rearrangement remains the most efficient and effective metht for synthesizing semibullvalene and its benzo and dibenzo derivatives. It is, indeed, surprising that this synthetic protocol has found so little utilization, especially in the subsequent transformation of products into useful complex target molecules. 

Die im Handel erhaltlichen Tricarbonyl-chrom-Solvens-Komplexe (Benzol, Benzoe-saure-methylester, Cycloheptadien, Toluol) sind gelbe bis rote Pulver, die aufier dem Cy-cloheptadien-Komplex an der Luft stabil sind. Bemerkenswert ist ihre Fahigkeit, 1,3-Diene unter 1,4-Addition in cls-Monoene umzuwandeln. Nicht konjugierte Diene konnen nach der Isomerisierung analog hydriert werden (s. Tab. 8, S. 51). 

CCRIS 2780 Dibenzo(a,d)cycloheptadien-5-one Di-benzo(a,d)cyclohepta(1,4)dien-5-one 5H-Dibenzo-(a,d)cyolohepten-5-one, 10,11-dihydro- Dibenzo-(b,f)cycloheptan-1-one Dibenzocycloheptenone Di-benzosuberan-5-one Dibenzosuberone 2,3 6,7-Di-benzosuberone Dibenzsuberone 10,11-Dihydro-5H-dibenzo(a,d)cyclohepten-5-one 10,11 -Dihydrodibenzo-... 

In the two antidepressants (imipramine and maprotiline), the bioisosterism is geometrical insofar that the dihedral angle a. formed by the two benzo rings is comparable a = 65° for the dibenzazepine and oi = 55° for the dibenzo-cycloheptadiene. ° This same angle is only 25° for the neuroleptic phenothiazines and the thioxanthenes. In these examples the part of the molecule modified by isosterism is not involved in the interaction with the receptor. It serves only to position correctly the other elements of the molecule. 

At still higher temperatures, 1,2-benzocycloheptatriene gives naphthalene, and both a- and /3-methylnapthalene and l,2-benzo-l,3-cycloheptadiene apparently by a radical chain process. 

Benzo-l-thia-5-aza-4,6-cycloheptadienes Thioethers from ethylene derivatives... 

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