Trans-1,3,8-nonatriene

Ziegler polymerization of, 44 trans-1,3,8-Nonatriene polymers of, 85 Norbornadiene... 

All of-cyclononatriene (53) cyclizes in the predicted disrotatory manner at measurable rates at 25-50°C to the bicyclic diene 54.115 The nine-membered ring is large enough to accommodate a trans double bond trans-cis-cis-cyclo-nonatriene (55), obtained by conrotatory photochemical opening of 54, cyclizes to the trans fused bicyclononadiene 55.116... 

This model also predicts that selectivity for the tranr-fused cycloadducts in nonatriene (n = 0) or deca-triene (n = 1) cyclizations should increase as size of the coefficients at C 2)IC S + n) are increased relative to those at C(l)/C(9 + n), that is, as the polarization of the dienophile or diene is increased. Tables 1 and 2 summarize results of intramolecular Diels-Alder reactions that provide a test of this propo-gai.24.25 it ig tiiat an electron-releasing Et N group at C(9) of the nonatrioioate system leads to a substantial increase in selectivity for the trans-fased product (compare entries 4-6, Table 1). Increased trans stereoselectivity also occurs with C(9)-alkoxy-substituted nonatrienes. A similar effect... 

CO Me group increases trans selectivity by only 0.1 kcal mol in the decatriene series (compare entries 1-3, Table 2) versus ca. 1.3 kcal mol with the nonatrienes, the additional increases in selectivity due to the COMe and CHO activating groups are comparable in the two series 0.6-0.7 kcal mol for COMe and 0.3-0.4 kcal mol for CHO. ... 

Similar nonbonded interactions occur between C(4) and C(7) substituents in the c/s-fused 1,6,8-nona-triene transition state (Figure 13). ° The very hi trans selectivity exhibited by trienes (42), (43), (44) and (46) is striking in view of the data summarized in Figure 2 for less highly substituted systems. The results with (44) and (45) imply that the extent of destabilization of the c/r-fused transition state depends on the steric requirements of the C(7) substituent, a conclusion also supported by other examples cited in the references. Nevertheless, these interactions are large enough to reverse the stereoselectivity of the IMDA reactions of internally activated nonatrienes (44) and (47) relative to the usually observed cis manifold (compare (5) and (7), Figure 2). 

Doubly activated all-carbon nonatrienes do not, however, exhibit as good selectivity for the trans-fused product as do trienes like (86) and (89) P. D. Williams and E. LeGoff, Tetrahedron Lett., 1985, 26, 1367. 

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). 

Other carbonyls cis-4-heptenal, trans,cw-2,6-nonadienal, 2,5-octadienal, 2,4,6-nonatrienal, 2,4,7-decatrienal, l-penten-3-one, l-octen-3-one,tra/ts,cw-3,5-octadien-3-one,3,5-undecadien-3-one, 1-octen-... 

Which double bond(s) in nerolidol and 4,8-dimethyl-1,3,7-nonatriene can exist as cis-trans isomers ... 

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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