Preparation and Properties of Conjugated Cyclic Polyolefins

Cycloheptatriene.—Synthesis. 7-Norbornadienol, available by saponification of 7-acetoxynorbornadiene, undergoes rapid base-catalysed rearrangement to the tropyl system. The mechanism suggested involves a 1,3-sigmatropic shift with inversion to 

Dimethyl heptalene-l,2-dicarboxylate (105) is the major product of the reaction between azulene and dimethyl acetylenedicarboxylate in the absence of acid. No heptalene is obtained if acid is present. Cyclopent[c,d]azulene reacts with dimethyl acetylenedicarboxylate to give [2 + 2] adducts which undergo cyclobutene ring 

3-Hexamethylene-bridged cycloheptatrienes have been prepared. Thus cyclo-dodecane-l,5-dione was cyclized by base to bicyclo[6,4,0]dodec-l(8)-en-9-one, which was reduced to the alcohol and converted into 13-bromobicyclo[6,4,l]trideca- 

12- triene by addition of dibromocarbene and thermal ring expansion. The 13-bromobicyclo[6,4,l]trideca-8,10,12-triene was reduced to bicyclo[6,4,l]trideca- 

12- triene by LiAlH, was converted into the 13-methyl derivative by methyl-lithium, and was oxidized to the bridged tropone (111) by chromium trioxide-pyridine. Attempts to convert 13-bromobicyclo[6,4,l]trideca-8,10,12-triene into a tropylium salt were unsuccessful, and (111) was not protonated on the carbonyl oxygen by trifluoroacetic acid.  

Cycloheptatriene.—Synthesis. Details have been published on the preparation of specifically substituted cycloheptatrienes by the cycloadditon of cyclopropenes to thiophene-1,1-dioxides followed by expulsion of S02. Substituted tropones have been obtained from the furan adducts of bromo-oxyallyl cations e.g. treatment of l,l,3,3-tetrabromo-4-methylpentan-2-one with di-iron nonacarbonyl in the presence of furan gave adduct (141) which was converted into a-thujaplicin (142). Acid hydrolysis of the norbornyl ketal (143) followed by warming to 70 C gave 7,7-dimethyl-cycloheptatriene.  

Kuroda, M. Funamizu, Y. Kitahara, and T. Asao, Tetrahedron Letters, 1975, 3197. 

) have been prepared by bis-condensations between the appropriate pyrrole bis-aldehyde and substituted acetone l,3-dimethyl-2/f-cyclohepta[c]pyrrol-6-one (148 R = H, R = R = Me, X = H) was then converted into 6-ethoxy-l,3-dimethyl-2-aza-azulene,  

Treatment of the tricyclic dienones (149) with l,5-diazabicyclo[5,4,0]undec-5-ene (DBU) gives the 3,4-benzocycloheptadienone (150). The mechanism suggested involves the formation and selective aromatization of isomeric fused cyclohexadiene-cyclo-heptatriene systems via the norcaradiene tautomer (151), The polycyclic nitriles (152) fragmented on treatment with pyridinium acetate to give the substituted cyclo- 

Oxymercuration of iV-benzyl-9-azabicyclo[4,2,2]deca-2,4,7-triene with mercury(ii) acetate in aqueous THF gave the cycloheptatriene aldehyde (156 R = CHO R2 = H) similarly (157) gave (156 R = H, R = CHO).  

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