Trans-bicyclo nonatriene

Thus, cis,trans,cis,cis-l,3,5,7-cyclononaXcirsiQnQ could be trapped during the thermolysis of the 6.1.0 triene. Subsequently it was found that this tetraene could be trapped with high concentrations of TCNE in a 2 + 2 fashion with a rate independent of TCNE concentration, which indicates rate-determining formation of the tetraene.Adducts of this tetraene were isolated earlier, and these were subsequently shown to be of the trans stereochemistry. Further, it was also found that the syn and anti isomers of 9-deuterio-cw-bicyclo[6.1.0]nonatriene interconvert prior to the isomerization to the dihydroindenes. The most likely pathway to the tetraene is a divinylcyclopropane 3,3-shift to bicyclo[5.2.0]nona-2,5,8-triene followed by a conrotatory cyclobutene ring opening (Scheme 10.11). ... 

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). 

The compounds [9]annulenyl-M (26) can be obtained from (27) (Scheme 4) in processes which involve electron transfer to give bicyclo[6,l,0]nonatriene radical anions, which then undergo stereoselective ring opening. Values of AG for the topomerization and isomerization [steps (h) and (c), Scheme 4, respectively] of cis,cis,cis,trans-(26) were 22 and 29.0—34.8 (dependent on M+) kcalmol", respectively. The compounds [17]annulenyl-M (M = Li, Na, or K) were also produced. Treatment by BuLi-TMED of cyclo-octa-1,5-diene and cyclo-octa-l,3,6-triene (but not cyclo-octa-1,3-diene nor cyclo-octa-1,3,5-triene) are converted into QHa -,2(Li TMED)+. C N.m.r, spectra of QH4Me,M (M = Li or K) in monoglyme were recorded. ... 

Cycloadditions of TCNE with cyclopropylethylenes, in which new bonds to the cyclopropane carbons form, have been reported further. Bicyclo[6,l,0]-nonatriene and the eJco-9-chloro-derivative undergo cycloaddition with TCNE but, though the cyclopropane opens, the stepwise polar additions are across C-3—C-4 to give adducts (424) see also p. The structures of (424) have been proven by 2f-ray crystallography and the trans junction was confirmed in both cases. 

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