Magnetic La0.7Sr0.3MnO3 nanoparticles: recyclable and efficient catalyst for ultrasound-accelarated synthesis of 4H-chromenes, and 4H-pyrano[2,3-c]pyrazoles

Nano magnetic complex lanthanum strontium magnesium oxide La0.7Sr0.3MnO3 (LSMO) has been explored as an efficient and recyclable catalyst to effect the one-pot three-component condensation reactions between aromatic aldehydes, malononitrile and 5,5-dimethyl-cyclohexane-1,3-dione, or 3-methyl-1-phenyl-2-pyrazolin-5-one in EtOH under ultrasound irradiation conditions. 2-Amino-5-oxo-5,6,7,8-tetrahydro-4H-chromenes and 1,4-dihydropyrano[2,3-c]pyrazol-5-yl cyanides were respectively synthesized from these reactions in high yields. This nano-catalyst can be easily recovered via magnetic concentration and reused without any significant drop in its catalytic activity. Magnetic La0.7Sr0.3MnO3 nanoparticles have been explored to efficiently catalyze the one-pot condensation of aromatic aldehydes, malononitrile and 5,5-dimethyl-cyclohexane-1,3-dione, or 3-methyl-1-phenyl-2-pyrazolin-5-one in EtOH under ultrasound-irradiation conditions. As a result, 2-Amino-5-oxo-5,6,7,8-tetrahydro-4H-chromenes and 1,4-dihydropyrano[2,3-c]pyrazol-5-yl cyanides were produced respectively in excellent yields. High efficiency, easy workup, high yields, use of cost-effective and non toxic catalyst are the main merits of this method.