Magnesium oxide (MgO) as a highly effective heterogeneous base catalyst effectively catalyzes the three component reaction of aryl aldehydes, malononitrile and a-hydroxy or a-amino activated C-H acids such as 1,3-cyclohexanedione, dimedone, 4-hydroxy-6-methylpyrone, 4-hydroxycoumarin, 1,3-dimethylbarbituric acid and 1,3-dimethyl-6-amino uracil to the formation of the corresponding pyran annulated heterocyclic systems. The catalyst is inexpensive and easily obtained, stable and storable, easily recycled and reused for several cycles with consistent activity.

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Magnesium oxide (MgO) effectively catalyzes the three-component reaction of aldehydes, amidine systems, and malononitrile or ethyl cyanoacetate to form 4-amino-5-pyrimidine carbonitrile and pyrimidinone derivatives, respectively. The salient features of this method include high conversions, short reaction times, cleaner reaction profiles, and the use of inexpensive and readily available catalyst.

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Magnetically separable Fe 3 O 4 nanoparticles were used as an environmental friendly catalyst for the synthesis of mono-and bis-tetrahydro-4H-chromene and mono-and bis-1,4-dihydropyridine derivatives via three-component reactions of aromatic aldehydes and malononitrile with cyclic b-dicarbonyls or cyclic benaminoketones respectively. These reactions were carried out in EtOH and at reflux. Fe 3 O 4 nanoparticles can be magnetically separated from the reaction mixture by a magnet and recycled without significant loss of catalytic activity.

Ultrasound irradiation can promote the 1,3-dipolar cycloaddition reaction of 2-chloropyridinium ylides with 2-benzylidenemalononitrile or 2,2'-(1,4-phenylenebis(methanylylidene))dimalononitrile, to afford the indolizine and bis-indolizine derivatives respectively. While the reaction of pyridinium ylides with 2-benzylidenemalononitrile or 2,2'-(1,4-phenylenebis(methanylylidene))dimalononitrile under ultrasound irradiation provided, in an unusual manner, cyclopropane and bis-cyclopropane derivatives, respectively. These cycloaddition and cyclopropanation reactions were carried out in the presence of triethylamine, in acetonitrile, at room temperature.

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