A parallel, efficient, and greener synthesis of functionalized azomethines of hydrazides catalyzed by in-situ generated carbonic acid (CO2(g) in water)

[Display omitted] •Parallel, efficient, rapid, and greener azomethines synthesis of isoniazid.•in-situ generated carbonic acid (CO2(g) in water) as catalyst.•Carbonic acid (H2CO3) as a economically and environmentally greener alternative.•Broad substrate scope, high yields, short reaction time, and simple workup procedure. This report provides an efficient, environment-friendly, and greener approach to synthesizing azomethines using carbonic acid (H2CO3) as a catalyst formed by passing dry ice (CO2 gas) in water. Carbonic acid is a nontoxic, greener, and readily available catalyst. Various aldehydes reacted well with isoniazid in shorter reaction time in EtOH: water (1:1) as a greener solvent at room temperature. Immersing CO2 (g) in the reaction mixture incorporated to generate carbonic acid provides economic and environmental benefits by accessing the reaction at room temperature. The key benefits of the method are shorter reaction time, higher product yield, and a hassle-free and straightforward experimental process under mild reaction conditions.