A new general synthesis of hydroxy- and methoxy-isoflavanones

Abstract

A new general synthesis of hydroxy-(5e–h) and methoxy-(5a–d) isoflavanones has been accomplished in overall yields of 47–73% from the corresponding 2-hydroxydeoxybenzoins (1a–h). The first step involves reaction with appropriate amounts of ethoxymethyl chloride in the presence of dry K₂CO₃ and acetone, which gives the corresponding α-hydroxymethyldeoxybenzoins (4a–d) and (4i–l). The explanation for the formation of unexpected alcohols has been provided on the basis of an elimination–addition mechanism. Subsequent refluxing with 4% aqueous ethanolic Na₂CO₃ afforded protected isoflavanones (5a–d) and (5i–l) respectively. Final removal of the ethoxymethyl groups of (5i–l) with 10% MeOH–HCl afforded the corresponding hydroxyisoflavanones (5e–h).