Novel combinatorial approach to the synthesis of dihydropyridine (quinoline) based merocyanine dyes

A novel, efficient, two-step approach to the synthesis of merocyanine dyes was developed. Initially, N-substituted picolinium salts were formylated with N,N-dimethylformamide dimethyl acetal to produce enamine derivatives. Then a series of merocyanine dyes were obtained by the high-yield reaction between the enamines and various active methylene compounds. The described reactions, carried out in mild conditions, provide access to the synthesis of a wide range of dyes. This innovative method enabled the synthesis of a number of new merocyanine dyes and increased the yields of the known compounds.