Hantzsch pyridine synthesis using hydrotalcites or hydrotalcite-like materials as solid base catalysts

Multicomponent one-pot synthesis of Hantzsch dihyropyridine (DHP) was achieved by the condensation of benzaldehyde, ethyl acetoacetate and ammonium acetate at room temperature using environmentally friendly as-synthesised medicinally acceptable hydrotalcites (HT) and hydrotalcite-like (HT-like) materials as solid base catalysts. The multifunctional activity of these materials is again proved by this important reaction. Among the catalysts screened, MgAl2-HT (Mg/Al atomic ratio = 2.0) showed maximum yield (61% in 6.5 h using acetonitrile as solvent). We propose that the high activity of this catalyst may be attributed to cooperative contribution of acid–base bifunctional sites. The versatility of these materials was checked by employing various aldehydes (acyclic, cyclic and aromatic) which showed reasonable yields of DHPs over MgAl2-HT. To our knowledge, this is the first report wherein HT and HT-like materials performed as catalysts for this multicomponent reaction and also the first case of employing a solid base catalyst for DHP synthesis.

Graphical abstractMulticomponent one-pot synthesis of Hantzsch dihyropyridine (DHP) was achieved at room temperature for the first time using environmentally friendly as-synthesised hydrotalcites (HT) and hydrotalcite-like (HT-like) materials as solid base catalysts.Figure optionsDownload full-size imageDownload as PowerPoint slide