Uncatalyzed Synthesis of Arylmethylene[bis(5,5-dimethyl-3-hydroxy-2-cyclohexene-1-ones)] in Hot Water by Domino Knoevenagel/Michael Reactions

A simple and ecofriendly method was developed for the synthesis of arylmethylene[bis(5,5- dimethyl-3-hydroxy-2-cyclohexene-1-ones)] from the reaction of 5,5-dimethylcyclohexane- 1,3-dione and aromatic aldehydes in an aqueous media without any catalyst via Knoevenagel condensation followed by rapid Michael addition. No cyclization product was down to convert these enolic forms to xanthene derivatives. Diverse aromatic aldehyde including electron-withdrawing (such as nitro group) groups or electron-donating groups (methoxy group) was used to give the corresponding dienolic forms successfully. This method provided several advantages such as simple work-up procedure, high yield, short reaction time and environmentally friendly nature.