Synthesis of unsymmetrical 1,4-dihydropyridine derivatives in ionic liquid and inference on the formation mechanism of furopyridines

Aromatic aldehydes,methyl acetoacetate,ethyl acetoacetate,ammonium acetate,ethyl 4-chloroacetoacetate as materials,eight unsymmetrical 1,4-dihydropyridine derivatives were synthesized in ionic liquid [bmim]oh in short time with the 60%-90% yield,and the ionic liquid could be utilized for 5 times repeatedly with the no decrease of the yield,four of products [3(a-d)] (see in table-1) were synthesized through knoevenagel and michael addition reaction,and another four furopyridines [3(e-h)] (see in table-2) through one-pot synthesis whose formation mechanism being different from that of [3(a-d)] was first inferred.