Synthesis of New Hydroxy‐2‐styrylchromones

Hydroxy‐2‐styrylchromones 5a − i were prepared by debenzylation of benzyloxy‐2‐styrylchromones 3a − i , which were synthesised by the Baker−Venkataraman method. The last step of this method, the cyclodehydration 5‐aryl‐3‐hydroxy‐1‐(2‐hydroxyaryl)‐2,4‐pentadien‐1‐ones 2a − i , was carried out with a catalytic amount of iodine, or p ‐toluenesulfonic acid, in DMSO. Benzyloxy‐3‐cinnamoyl‐2‐styrylchromones 4a − f were obtained as by‐products in both procedures, but the latter procedure gave benzyloxy‐2‐styrylchromones 3a − i in better yields. The structures of all new compounds were established by extensive NMR studies. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)