Auwers synthesis

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| Name = Auwers synthesis

| Type = Coupling reaction

| NamedAfter = Karl von Auwers

| Section3 = {{Reactionbox Identifiers

| RSC_ontology_id = 0000474

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The Auwers synthesis is a series of organic reactions forming a flavonol from a coumarone. This reaction was first reported by Karl von Auwers in 1908.K. Auwers, K. Müller, "Umwandlung von Benzal-cumaranonen in Flavonole", Ber. Dtsch. Chem. Ges., 41, 4233–4241 (1908) ({{doi|10.1002/cber.190804103137}}).K. v. Auwers, P. Pohl, "Über die Umwandlung von Benzalcumaranonen in Flavonole", Liebigs Ann. Chem., 405, 243–294 (1914) ({{doi|10.1002/jlac.19144050302}}).K. v. Auwers, P. Pohl, "Eine Synthese des Fisetins", Ber. Dtsch. Chem. Ges., 48, 85–90 (1915) ({{doi|10.1002/cber.19150480114}}).K. v. Auwers, "Zur Bildung von Flavonolen aus Benzal-cumaranonen", Ber. Dtsch. Chem. Ges., 49, 809–819 (1916) ({{doi|10.1002/cber.19160490188}}).K. v. Auwers, E. Auffenberg, "Über Cumaranone und Hydrindone", Ber. Dtsch. Chem. Ges., 52, 92-113 (1919) ({{doi|10.1002/cber.19190520114}}).

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The first step in this procedure is an acid catalyzed aldol condensation between benzaldehyde and a 3-cyclooxapentanone to an o-hydroxychalcone. Bromination of the alkene group gives a dibromo-adduct which rearranges to the flavonol by reaction with potassium hydroxide.