Tricyclo nonatriene

Trapping of less stable valence tautomers with benzylideneacetone(tricarbonyl)iron [BDA-Fe(CO)3] was applied to bicyclo[6.1.0]nonatriene (40a) and its i>> -9-methyl derivative (40b). Reaction with BDA-Fe(CO)3 gave three products, one of which was a complex of tricyclo[4.3.0.0 ]nona-2,4-diene 41. As the major product tricarbonyl(tricyclo[4.3.0.0 ]... 

After subtraction of the distribution of labels obtained from the dominant pathway, the remaining distribution is not easily accounted for. Ruled out are pathways that involve formation of c/5 -bicyclo[6.1.0]nonatriene by a 1,3-shift of the one carbon bridge which gives the dihydroindene (see Section 2.1) or cyclization back to a cyclobutene followed by 1,3-shift of the cyclobutene moiety to a tricyclo[5.2.0.0 ]nona-3,7-diene which ring opens to the dihydroindene. 

The same mixture of compounds was obtained from pyrolysis of trans-, 9-dihydroindene. Since the major products were not obtained upon pyrolysis of bicyclo[6.1.0]nonatriene, it is clear that this material and bicyclo[5.2.0]nonatriene and all c/ -cyclononatetraene or its c,t,c,c or t,c,c,c isomer are not involved in these thermal isomerizations (see Section 2.1). It would appear reasonable that 1,5-hydrogen shifts could convert the rra/i5 -8,9-dihydroindene to the major product and ultimately to the other products however, not clear is how the tetracyclononene is converted to rra/i5 -8,9-dihydroindene. This latter material could undergo a concerted or stepwise homo-3,3-shift to tricyclo[4.3.0.0 ]nona-4,7-diene, but progress from there to fra/i5 -8,9-dihydroindene is not obvious (Scheme 10.25). 

Tricyclo[3.2.2.0 " ]nonatriene (LXII) affords bicyclo[4.2.1] nonatriene (LXIII) in quantitative yield as a result of reaction with chlorodicarbonyl-rhodium(I) dimer. By contrast, benzene and allylbenzene are formed on... 

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