Fast and efficient synthesis of flavanones from cinnamic acids

<p>A fast and efficient synthesis of flavanones from cinnamic acids in three steps has been developed. First, the cinnamic acid was converted to cinnamyol chlorides using SOCl<sub>2</sub>. The acid chlorides were then treated with substituted phenols in BF<sub>3</sub> · OEt<sub>2</sub> to furnish corresponding chalcones in 42(75% yields. Base-catalyzed cyclization of the chalcones at room temperature afforded corresponding flavones in 85–95% yields. The conversion of the cinnamic acid derivatives to corresponding chalcones was found to be sensitive to the position and nature of the substituents on the aromatic rings.</p>