An efficient four-component protocol for synthesis of poly-substituted pyridines with SiO₂ as a robust recyclable catalyst

A four-component protocol for the development of poly-substituted pyridines derivatives by using SiO2 as a recycle catalyst. The protocol offers good to excellent yields (85%-95%) under milder conditions in a short reaction time of 2-3 hours. The use of a less expensive catalyst makes this protocol more convenient. SiO2 has been identified as a convenient catalyst for the synthesis and can be reused for up to three cycles.</p

Sulfonic acid–functionalized Wang resin (Wang-OSO₃H) as polymeric acidic catalyst for the ecofriendly multicomponent synthesis of polyhydroquinolines via Hantzsch condensation

<p>An efficient and green approach has been developed for the synthesis of polyhydroquinoline derivatives via Hantzsch condensation reaction directly from corresponding substituted aromatic and aliphatic aldehydes, β-keto compounds, active methylene compounds, and ammonium chloride using recyclable polymer-supported sulfonic acid catalyst under aqueous conditions. Environmental acceptability, operational simplicity, low cost, excellent functional group compatibility, and high yields are the important features of this protocol.</p