Synthesis of Flavones and γ-Benzopyranones Using Mild Sonogashira Coupling and 18-Crown-6 Ether Mediated 6-endo Cyclization

An efficient method for the synthesis of flavones and γ‐benzopyranones has been developed utilizing a mild Sonogashira coupling and 18‐crown‐6 ether mediated 6‐endo cyclization of o‐alkynoylphenyl acetates. By using this strategy, flavones and γ‐benzopyranones bearing electron‐donating groups, halogens, and simple alkyl substituents were synthesized in satisfactory yields. A facile, mild, and selective method for the synthesis of flavones and γ‐benzopyranones is reported. o‐Alkynoylphenyl acetates were obtained from either acyl chloride derivatives or substituted salicylates. Upon removing the acetate group, flavones and γ‐benzopyranones were synthesized within 15 min with the aid of 18‐crown‐6 ether. A library of flavones and γ‐benzopyranones was established.