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Synthesis 1988; 1988(5): 359-362
DOI: 10.1055/s-1988-27573
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New and Efficient Lewis Acid Catalysts in Intramolecular Ene Reactions

Lutz F. Tietze* , Uwe Beifuß
  • *Institut für Organische Chemie der Georg-August-Universität, Tammannstraße 2, D-3400 Göttingen, Federal Republic of Germamy
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Publication Date:
20 August 2002 (online)

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The thermal or Lewis acid catalyzed intramolecular ene reaction of the Knoevenagel adduct 3 from citronellal and dimethyl malonate affords the two diastereoisomeric dimethyl (5-methyl-2-trans-isopropenylcyclohexyl)malonates 4a and 4b. Anhydrous iron(III) chloride on basic alumina proved to be the best catalyst giving, at - 78°C, the two diastereoisomers 4a and 4b in a ratio of 98.8:1.2 in 92% yield.