Synthesis of New and Highly Functionalized 1,4‐Dihydropyridines and Spirooxindole Dihydropyridines Using L‐Proline as Efficient Catalyst

Recent advances in the multicomponent synthesis of heterocycles using tetronic acid

Tetronic acid, a versatile synthon, has been extensively investigated by numerous researchers in synthetic chemistry due to its crucial role in synthesizing heterocycles which makes this compound particularly advantageous in both pharmaceutical and biological fields. Various heterocycles can be synthesized using it as a precursor via multicomponent reactions (MCRs). Dicarbonyl groups can be considered the building blocks and key structural motifs of a wide range of natural compounds, which may contain different functional groups in the synthesis of heterocyclic frameworks. This review covers the literature from 2017 to 2022, and it encompasses the different one-pot protocols for synthesizing a variety of heterocyclic molecules.

Loading of g-C3 N4 on Core-Shell Magnetic Mesoporous Silica Nanospheres as a Solid Base Catalyst for the Green Synthesis of some Chromene Derivatives under Different Conditions

Using heterogeneous basic catalysts has a great importance in chemical reactions because of their advantages (such as easy separation and thermal stability at harsh conditions) over homogeneous catalysts. In this study, magnetic mesoporous silica nanoparticles (mSiO₂) containing graphitic carbon nitride layers (mSiO₂/g‐C₃N₄(x)) were fabricated through a facile process (x signifies the amount of melamine applied during synthesis). Graphitic carbon nitride layers were decorated on mSiO₂ by calcination of immobilized melamine (as graphitic carbon nitride precursor) on mSiO₂ in the last step of catalyst synthesis. The structure of the prepared catalysts was confirmed using XRD, BET, FESEM, EDX, elemental mapping and TEM methods. The catalytic efficiency of the so‐obtained solid base composite was investigated for the synthesis of some dihydropyranochromenes and spiro‐dihydropyranochromenes under thermal and microwave conditions. Using mSiO₂/g‐C₃N₄(x) led to high yields under green conditions and in short reaction times and without a decrease in catalytic activity after four consecutive cycles.

Visible Light Mediated, Catalyst Free, One-Pot Convenient Synthesis of Dihydropyridines

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A simple, efficient and green protocol has been developed for the synthesis of polysubstituted dihydropyridines via one-pot, four-component reaction of aldehydes, arylamines, dialkyl acetylenedicarboxylate, and malononitrile. The reaction was proceeded at room temperature in the absence of catalyst in aqueous ethyl lactate under visible light irradiation. The main advantages of the present approach are mild reaction condition, high yield, no column chromatography, clean reaction profile, environmentally friendly and sustainable from the economic point of view