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Communication | Regular issue | Vol 36, No. 8, 1993, pp.1725-1728
Published online, 1st January, 1970
DOI: 10.3987/COM-93-6397
Synthesis of Methyl 2-Cyano-(1,2-dimethylcyclohepta[b]pyrrol-6-ylidene)acetate. A Steric Effect to Accelerate the Geometrical Isomerism of the Exocyclic C=C Bond of Heterocycle-fused Heptafulvenes

Yukari Ikeda, Bing Zhu Yin, Nobuo Kato, Akira Mori,* and Hitoshi Takeshita*

*Instituete of Advanced Material Study, Kyushu University, 6-1, Kasuga-koen, Kasuga 816-8580, Japan

Abstract

The rotational barriers of the exocyclic C=C bonds of heptafulvenes condensed with furan, pyrrole, and thiophene rings were largely dependent on the steric repulsion around the exocyclic C=C bonds; newly synthesized methyl 2-cyano-(1,2-dimethylcyclohepta[b]pyrrol-6-ylidene)acetate and its furanylidene analogue revealed higher energy barriers than the corresponding methyl 2-cyano-(1,2-dimethylcyclohepta[b]pyrrol-8-ylidene)acetate and the furan derivatives.