Facile and Metal‐Free Synthesis of Isoflavones Using α‐Aryl‐β,β‐Ditosyloxy Ketones

Abstract

Considering the drawbacks associated with available synthetic methodologies of isoflavones, herein we have reported a metal‐free and eco‐friendly approach to these natural products. In the present study, we have carried out the synthesis of eight isoflavone derivatives 7a–7h using α‐aryl‐β,β‐ditosyloxy ketone protocol. Initially, we have protected the 2’‐hydroxy group of respective chalcone moiety in order to remove its interference under reaction conditions. The protected chalcones were then subjected to 1,2‐aryl migration by being treated with hydroxy(tosyloxy)iodobenzene (HTIB) reagent in a non‐nucleophilic solvent (CH₂Cl₂). This migration furnished the formation of α‐aryl‐β,β‐ditosyloxy ketones via C−C bond formation from their corresponding chalcones in moderate to good yields (55–82 %). The ambiguity regarding the exact molecular structure of the α‐aryl‐β,β‐ditosyloxy ketones was examined through the single crystal X‐ray diffraction data. At last, the synthesis of isoflavones was carried out in moderate to good yields (50–80 %) by performing the reaction of α‐aryl‐β,β‐ditosyloxy ketones with sodium hydroxide in aqueous methanol.