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Synthesis 1989; 1989(7): 501-505
DOI: 10.1055/s-1989-27300
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A Simple and Convenient Synthesis of 5-Alkyl-Substituted 3-Isopropenyl- and 3-Acetyltropolones

Kimiaki Imafuku* , Kiyomi Arai
  • *Department of Chemistry, Faculty of Science, Kumamoto University, Kurokami, Kumamoto 860, Japan
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Publication Date:
17 September 2002 (online)

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2-Alkyl-substituted 6,6-dimethylfulvenes 3a-d, prepared by alkaline condensation of alkylcyclopentadienes 2a-d with acetone, react with dichloroketene to give 2-alkyl-substituted 7,7-dichloro-4-isopropyl-idenebicyclo[3.2.0]hept-2-en-6-ones 4a-d. The cycloadducts 4a-d are hydrolyzed in aqueous acetic acid in the presence of sodium acetate to give 5-alkyl-substituted 3-isopropenyltropolones (2-hydroxy-3-isopropenyl-2,4,6-cycloheptatrienones) 5a-d. These 3-isopropenyltropolones 5a-d are hydrogenated on 5% palladium-charcoal to afford 5-alkyl-3-isopropyltropolones 6a-d and treated with hydrazoic acid to give 5-alkyl-3-acetyltropolones 7a-d.