Kostanecki acylation

The Kostanecki acylation is a method used in organic synthesis to form chromones or coumarins by acylation of O-hydroxyaryl ketones with aliphatic acid anhydrides, followed by cyclization. If benzoic anhydride (or benzoyl chloride) is used, a particular type of chromone called a flavone is obtained.



Mechanism
The mechanism consists of three well-differentiated reactions:
 * 1) Phenol O-acylation with formation of a tetrahedral intermediate
 * 2) Intramolecular aldol condensation to cyclize and to form a hydroxydihydrochromone
 * 3) Elimination of the hydroxyl group to form the chromone (or coumarin)



Examples

 * Alvocidib (flavopiridol)
 * Dimefline
 * Flavoxate