19152-36-4

118-93-4

120-14-9

79140-20-8

The method is applicable to compounds that do not contain free phenolic hydroxyl groups or when the phenolic hydroxyl groups are protected as methyl or benzyl ethers. The corresponding 2'-hydroxyacetophenone (10 mmol) was dissolved in anhydrous THF (25 mL), and NaH (25 mmol, 1 g 60% mineral oil dispersion) was added to the solution in batches under nitrogen protection with vigorous stirring. After the hydrogen release ceased, a corresponding solution of anhydrous THF (25 mL) with veratraldehyde (10 mmol) was added slowly and dropwise over a period of 15 minutes, followed by stirring of the reaction mixture at room temperature for 16 hours (unless otherwise indicated). Upon completion of the reaction, the mixture was carefully poured into ice water (100 mL) to quench the excess NaH and stirred until the hydrogen release stopped completely. The mixture was acidified with 25% HCl and subsequently extracted with ethyl acetate (3 x 50 mL). The organic layers were combined and washed sequentially with water (3 x 50 mL) and brine (50 mL) and then dried with anhydrous MgSO4. The solution was concentrated under reduced pressure to 1/3 of the original volume at 40 °C, then cooled at 0 °C for 12 h. The crystalline product was collected by filtration. The purity of 2'-hydroxychalcone obtained in this way is sufficient for most applications. Analytically pure samples require further purification by column chromatography. Good yields of chalcone can be obtained by this method. Additional product can be obtained by evaporating the solvent from the mother liquor and purifying by column chromatography.