Regioselective monobromination of (E)-1-(2′-hydroxy-4′,6′-dimethoxyphenyl)-3-aryl-2-propen-1-ones using bromodimethylsulfonium bromide and synthesis of 8-bromoflavones and 7-bromoaurones

A wide variety of monobrominated compounds 2a-l have been prepared in good yields from (E)-1-(2′-hydroxy-4′,6′-dimethoxyphenyl)-3-aryl-2-propen-1-ones (1a-l) through regioselective ring bromination using 1.5 equiv of bromodimethylsulfonium bromide (BDMS) at room temperature. Similarly, some of the 2′-hydroxychalcones can be converted directly into tribromides 3 or dibromides 4 by employing 4.0 equiv of BDMS under different reaction conditions which in turn can be transformed into 8-bromoflavones and 7-bromoaurones on treatment with 0.2 M ethanolic KOH solution. Mild reaction conditions, good yields and no chromatographic separation are some of the salient features of the present protocol.