Domino Reaction of 3-(2-Formylphenoxy)propenoates and Amines: A Novel Synthesis of 1,4-Dihydropyridines from Salicaldehydes, Ethyl Propiolate, and Amines

A novel synthesis of Hantzsch-type N-substituted 1,4-dihydropyridines from salicaldehydes, ethyl propiolate, and
amines has been developed. Salicaldehydes were treated with
ethyl propiolate in the presence of N-methylmorpholine to
give ethyl 3-(2-formylphenoxy)propenoates. Three equivalents of ethyl 3-(2-formylphenoxy)propenoates reacted with
1 equiv of amines under trifluoroacetic acid (TFA) catalyst
to furnish the corresponding N-substituted 1,4-dihydropyridines in good to excellent yields, recovering the starting
material salicaldehydes. A possible mechanism for the
domino process was proposed. Furthermore, the products can
be easily derived via further transformations and three of
them exhibited strong fluorescence (Φf = 0.36−0.63).