Chromones Kostanecki-Robinson synthesis

Kojic acid — see also Pyran-4-one, 5-hydroxy-2-hydroxymethyl-, 3, 611 acylation, 3, 697 application, 3, 880 occurrence, 3, 692 reactions, 3, 714, 715 with amines, 3, 700 with phenylhydrazine, 3, 700 synthesis, 3, 810 Kokusagine occurrence, 4, 989 Kokusaginine occurrence, 4, 989 synthesis, 4, 990 Koopmans theorem, 2, 135 Kostanecki-Robinson reaction chromone and coumarin formation in, 3, 819-821 mechanism, 3, 820 flavones, 3, 819... 

Although the literature refers to the formation of chromones/coumarins as the Kostanecki reaction (and often the Kostanecki-Robinson reaction) and the synthesis of flavones as the Allan-Robinson reaction, others have chosen to merge the two reactions and refer to both transformations as the Kostanecki-Robinson reaction. This section will follow the latter school of thought, and use the Kostanecki-Robinson (K-R) nomenclature. 

The synthesis of chromones by the Kostanecki-Robinson method frequently yields a 3-acetylchromone. This acetyl group forms a 1,3-diketone with the pyran carbonyl group and is therefore labile in an alkaline medium. Treatment with aqueous carbonate or other base removes such groups but has no effect on other acyl substituents, for example the 6-acetyl of 3,6-diacetyl-2-methylnaphtho[l,2- ]pyran-4-one (516). 

While the chromone moiety is found in several natural products, the Simonis chromone synthesis has not been exclusively used to prepare chromones. Other methods exist that are oftentimes more easily utilized, run under more mild conditions, or provide higher yields. For example, the Kostanecki-Robinson reaction has found application in this arena. However, alternative reaction types are not without their own issues therefore, the Simonis chromone synthesis remains a tool for the synthetic chemist. 

ROBINSON - ALLAN - KOSTANECKI Chromone Synthesis Synthesis of chromones or coumannes from o acyioxy aromatic ketones... 

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