Catalyst-free one-step green synthesis of novel N-heteroaryl-α-(4-amino-2-oxo-2H-chromen-3-yl)glycine derivatives via a Mannich reaction employing glyoxylic acid

An efficient and environmentally friendly method has been reported for one-pot, three-component synthesis of novel N -heteroaryl-α-(4-amino-2-oxo-2 H -chromen-3-yl)glycine derivatives from 4-aminocoumarin, glyoxylic acid monohydrate and heteroaryl amines without using any catalyst in EtOH as a reaction medium under heating condition. The reaction proceeded via a Mannich pathway, which involved the initial formation of a Schiff-base intermediate. This intermediate then underwent nucleophilic attack by 4-aminocoumarin, followed by a final tautomerization to produce the product in good to high yields. This method offers several advantages, including operational simplicity, easy work-up, environmentally friendly, catalyst-free conditions, short reaction times, broad substrate scope, and straightforward product purification without chromatography. The structures of the synthesized compounds were confirmed by spectroscopic analysis, including FT-IR, 1 H NMR, 13 C NMR, and mass spectrometry, all of which are consistent with the proposed structures.