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|Title:||Synthesis and Diatropicity of trans-10b,10c-Dimethylacenaphthyleno[1,2:e]-10b,10c-dihydropyrene: A Model Aromatic Molecule to Verify the Effect of Conjugation on the Diatropicity of an Annulene|
|Authors:||Lai, Y.-H. |
|Source:||Lai, Y.-H.,Chen, P.,Dingle, T.W. (1997). Synthesis and Diatropicity of trans-10b,10c-Dimethylacenaphthyleno[1,2:e]-10b,10c-dihydropyrene: A Model Aromatic Molecule to Verify the Effect of Conjugation on the Diatropicity of an Annulene. Journal of Organic Chemistry 62 (4) : 916-924. ScholarBank@NUS Repository.|
|Abstract:||The title compound 11 was synthesized from acenaphthenequinone in 11 steps with an overall yield of ca. 1.3%. Photochemical desulfurization of the thiacyclophanene 24 afforded the cyclophanene 28. Photochemical isomerization of 28 to the tetrahydropyrene derivative 32 followed by DDQ oxidation gave the desired dihydropyrene 11. Compound 11 is found to sustain only about 85% of the ring current of the parent dihydropyrene 1. On the basis of our results, a significant effect on the diatropicity of the 14π annulene in 11 due to its conjugation with a naphthalene moiety is verified. A correlation between theoretically calculated bond orders and experimentally observed coupling constants for selected bonds in 11 indicates that the inductive effect, relative to the resonance effect, plays a major role in the net effect of conjugation observed in 11. Among several derivatives of dihydropyrene 1, a linear relationship is observed for an empirical correlation between the methyl chemical shifts and the corresponding Dewar resonance energies associated with the benzenoid systems in conjugation with 1. This may serve as a method to estimate the resonance energies of other aromatic systems relative to that of benzene. Compound 11 underwent electrophilic nitration, acetylation, and bromination readily under mild conditions. The electrophiles reacted selectively with the dihydropyrene system in 11 and not the acenaphthylene moiety in conjugation.|
|Source Title:||Journal of Organic Chemistry|
|Appears in Collections:||Staff Publications|
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