Title: Anionic Cyclization of a Cross-Conjugated Enediyne
Abstract: Cross-conjugated enediynes cannot follow the Bergman cycloaromatization as it involves a methylenediyne moiety with only five pi e(-), insufficient for aromatization. Under reductive conditions the cyclization is made feasible by generating a product with a Hückel number of pi electrons. We illustrate this principle and demonstrate for the first time an anionic cyclization of a cross-conjugated enediyne that results in formation of a five-membered ring. 9-(3-Phenyl-1-phenylethynylprop-2-ynylidene)-9H-fluorene (3) was reduced by potassium to yield the dianion of 9-(3,4-diphenylcyclopenta-2,4-dienylidene)-9H-fluorene (4(2-)), which contains a cyclopentadienyl fragment, and oxidation with iodine yielded the unstable fulvalene 4.
Publication Year: 2002
Publication Date: 2002-03-20
Language: en
Type: article
Indexed In: ['crossref', 'pubmed']
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Cited By Count: 34
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