1-(5-Chloro-2-hydroxyphenyl)-3-(4-chlorophenyl)-2-propen-1-one → 6-Chloro-2-(4-chlorophenyl)-2H-1-benzopyran

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Reaction Steps

4,5'-Dichloro-2'-hydroxychalcone (7.32 g) was dissolved in ethanol (100 ml) and sodium borohydride (1.89 g) added in small portions. The reaction mixture was stirred for 1 hr at room temperature, evaporated to dryness, and diluted with water. The precipitated solid was filtered off, washed with water, and heated with acetic acid (100 ml) on the steam bath for 2 hr. The acetic acid was evaporated the residue dissolved in dichloromethane, and the solution washed sequentially with water, saturated sodium bicarbonate solution, and water, dried and evaporated. The residue was chromatographed on alumina, eluting with toluene, to give 4',6-dichloroflav-3-ene (3.84 g) as a colourless oil, identified by n.m.r. spectroscopy.

Provenance & Evidence