Synthesis of new substituted dihydroheptalene derivatives: SiO2- and base-catalyzed rearrangement of dimethyl trans-3,8-dihydroheptalene-3,8-dicarboxylate


Saracoglu N., Menzek A., Kinal A., Balci M.

CANADIAN JOURNAL OF CHEMISTRY-REVUE CANADIENNE DE CHIMIE, vol.79, no.1, pp.35-41, 2001 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 79 Issue: 1
  • Publication Date: 2001
  • Doi Number: 10.1139/cjc-79-1-35
  • Title of Journal : CANADIAN JOURNAL OF CHEMISTRY-REVUE CANADIENNE DE CHIMIE
  • Page Numbers: pp.35-41

Abstract

Dimethyl trans-3,8-dihydroheptalene-3,8-dicarboxylate (trans-3) isomerizes to dimethyl cis-3,8-dihydroheptalene-3,8-dicarboxylate (cis-3) upon treatment with SiO2. On the other hand, base-catalyzed reaction of trans-3 undergoes a direct 1,3-intramolecular proton shift to give 6 at room temperature in 5 min. Prolonged reaction time formed isomers 7 and 8 in a ratio of 4:1. AM1 calculations indicate that the isomer 8, which is formed as minor product, has a lower heat of formation (-99.34 kcal mol(1)) than that of the major isomer 7 (-92.05 kcal mol(1)). However, when a similar reaction was performed at 100 degreesC, the thermodynamically more stable isomer 8 was formed as the major product. Furthermore, cycloaddition reactions of these new dihydroheptalene derivatives 6 and 7 with different dienophiles have been studied. The mechanism has been discussed.