An efficient synthesis of 3-bromoflavones under solvent free conditions using grinding technique

Selective bromination of 1-(2-hydroxyphenyl)-3-phenylpropane-1,3-diones has been carried out with ammonium bromide and ammonium persulphate at room temperature using grinding technique under solvent free conditions to give 2-bromo derivatives which on cyclodehydration with p-toluenesulphonic acid under grinding conditions give 3-bromoflavones. Also, flavones on bromination using above mentioned conditions give 3-bromoflavones directly.