Environmentally benign syntheses of flavanones

Mild and environmentally benign methods for the syntheses of flavanones are described. The reaction of o-hydroxyacetophenones (1) and benzaldehydes (2) in water in the presence of DABCO at room temperature gave 3-hydroxy-1-(2-hydroxylphenyl)-3-arylpropan-1-ones (3a–i) as intermediates. Followed by an intramolecular dehydration of the 3a–i with the modified Mitsunobu’s reaction, the target flavanones (4a–i) were obtained. Moreover, the reaction of 1 and 2 at the same conditions but at reflux gave flavanones in one pot with good yields.