A catalyst- and solvent-free protocol for the sustainable synthesis of fused 4-pyran derivatives.

An efficient and cost-effective method was developed for the synthesis of two kinds of fused 4-pyran derivatives, namely, dihydropyrano[2,3-]pyrazole 4 and pyrano[3,2-]chromenone 6. The reactions of 3-methyl-1-phenyl-5-pyrazolone/4-hydroxycoumarin with aromatic aldehydes and ()--methyl-1-(methylthio)-2-nitroethenamine (NMSM), involving the Knoevenagel, Michael-addition, -cyclization and elimination reactions under thermal heating, afforded the desired products. The synthesized compounds were characterized by standard spectroscopic techniques.

Microwave irradiation: a green approach for the synthesis of functionalized -methyl-1,4-dihydropyridines.

An eco-friendly and cost-effective, microwave-assisted green approach has been developed for the synthesis of diverse functionalized -methyl-1,4-dihydropyridines (1,4-DHPs). This pseudo three-component reaction was carried out between two equivalents of ()--methyl-1-(methylthio)-2-nitroethenamine (NMSM) and one equivalent of aromatic aldehydes under microwave irradiation at 100 °C without catalyst and solvent. Short reaction times, avoidance of toxic solvents or expensive, metallic and corrosive catalysts and no need for column chromatographic purification are among the valuable features of the presented method.