Synthesis of Novel Bromo‐substituted Flavone‐like Troponoid Compounds from Oxidation Cyclization of 3‐Cinnamoyl‐5,7‐dibromotropolones Using I 2 /DMSO/H 2 SO 4 System

A convenient method to obtain a series of bromo‐substituted flavone‐like troponoid compounds 6,8‐dibromo‐2‐arylcyclohepta[ b ]pyran‐4,9‐diones 3a–3s by oxidation cyclization of the readily available intermediates 3‐cinnamoyl‐5,7‐dibromotropolones 2a–2s using I 2 /DMSO/H 2 SO 4 system was realized. Compounds 2a–2s were obtained from the aldol reaction of 3‐acetyl‐5,7‐dibromotropolone 1 with various benzaldehydes. Compounds 2a–2s and 3a–3s are novel and their structures were supported by IR, 1 H NMR, MS and elemental analyses.