Efficient organocatalyzed solvent-free selective synthesis of conjugated enones

A series of conjugated dienones and enones were synthesized by a reaction of both conjugated and simple aldehydes, respectively, with 1,3-dicarbonyl compounds and aldehydes under solvent-free conditions at room temperature in the presence of 10 mol % of l-proline as catalyst. The selective formation of one isomer was observed exclusively with most of the 1,3-dicarbonyl compounds and aldehydes. The most commonly formed xanthene derivative from the cyclic diketones is inhibited with our protocol, with the exclusive formation of conjugated dienones only.