Annulenes and Azulenes

The cis,trans,cis stereochemistry of c/i, /r i i,CM-cyclodeca-2,4,8-triene-1,6-dione (69) has been confirmed by X-ray analysis. The molecule, which is the diketo-tautomer of l,6-dihydroxy[10]annulene, is non-planar, and 

The striking alternation of bond lengths in 7-methoxycarbonyl-aitf(-1,6 8,13-bismethano[14]annulene (70) [1.33—1.49 A] confirms the polyenic 

Gramaccioli, A. Mimun, A. Mugnoli, and H. Simonetta, Chem. Comm., 1971, 796. 

An interesting property of l,6-methano[10]annulene is the influence of bridge-substituents on the stability of the aromatic system. For example, there is chemical and spectroscopic evidence in favour of the existence of a direct 1—6 bond in the 11,11-dimethyl derivative, thus producing the bisnorcaradiene structure (73). In contrast, the 11,11-difluoro-compound 

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The cycloaddition reactions of acetylenes with annulenes and azulenes has been studied and can lead to a variety of products (Scheme 80). ... 

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