Facile synthesis of rubiadin by microwave heating
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Rubiadin (4) (1,3-dihydroxy-2-methylanthraquinone), which is one of the natural dyes from the roots of Rubiaceae, was synthesized from phthalic anhydride (1) and 2,6-dihydroxytoluene (3) by two reaction steps, that is, a Friedel-Crafts reaction with AlCl3 and a cyclization with H2SO4/HBO2. Microwave heating resulted in remarkable acceleration of the reaction rate in the first reaction, and had an effect in reducing the reaction time and increasing the yield of rubiadin (4) in the second reaction.
Key wordsSynthesis Rubiadin Hydroxyanthraquinone Microwave Friedel-Crafts acylation
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