The synthesis of kermesic acid by acetylation-aided tautomerism of 6-chloro-2,5,8-trihydroxynaphtho-1,4-quinone |
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Authors: | Steve J Bingham John HP Tyman |
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Institution: | a Department of Chemistry, Brunel University, Uxbridge, Middlesex UB8 3PH, UK b Laboratories of European Colour plc, Nathan Way, London SE18, UK |
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Abstract: | Methodology has been sought towards obtaining a 2-chloro-1,4-naphthoquinone bearing hydroxyl groups in the adjoining ring for obtaining either kermesic or carminic acids. In the first of these objectives, kermesic acid has been synthesised from 6-chloro-2,5,8-trihydroxynaphtho-1,4-quinone by the regioselective cycloaddition of the 1,2-diacetate formed by its acetylation-aided tautomerism and cycloaddition with (E)- and (Z)-3-alkoxycarbonyl-2,4-bis(trimethylsilyloxy)penta-1,3-dienes. The parent unacetylated quinone resists cycloaddition. |
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