A convenient and easy synthesis of 4-arylidene-3-phenylisoxazol-5-ones by the three-component reaction of hydroxylamine, ethyl benzoylacetate and aromatic aldehydes in the presence of DABCO in refluxing ethanol is reported.

Commercially available potassium hydroxide (KOH), a simple base, was found to be a catalyst for tandem cross-aldol condensation between cyclic ketones and aromatic aldehydes leading to a fast and easy synthesis ofα,α-bis (substituted-arylidene) cycloalkanones in the shortest times of all previous methods. The reaction of aryl aldehydes with five and six-membered cyclic ketones afforded excellent yields after few seconds in most cases. The reaction conditions were compatible with various electron withdrawing and electron donating substituents,e.g.Cl, F, NO2, OMe, Me and NMe2.

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Crossed aldol condensation of aromatic aldehydes with cyclic ketones in the presence of catalytic amount of NH 4 H 2 PO 4 /SiO 2 (as a safe, green, and cheap heterogeneous catalyst) under solvent-free condition afforded a,a´bis(substituted-benzylidene) cycloalkanones in high yields. This method is general with respect to all types of aromatic aldehydes and is an eco-friendly procedure. And the catalyst is easily prepared, stable, reusable, and efficient under the reaction conditions.

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