SnCl₂·2H₂O as a precatalyst in MCR: Synthesis of pyridine derivatives via a 4-component reaction in water

For the first time SnCl₂·2H₂O has been identified as a convenient precatalyst for the synthesis of pyridine derivatives via an MCR in water. The 4-component reaction of alkyl/(hetero)aryl aldehydes, β-keto esters (or 1,3-diketones), anilines, and malononitrile afforded a range of new polysubstituted pyridines including 4-alkyl/heteroaryl derivatives in 78-91% yields. The use of less expensive catalyst in aqueous media and good yields of products with wider substrate scope are the key features of this methodology.