Tandem Protocol for the Synthesis of Pyrano[3,2-c]quinolone Derivatives Using Taurine as a Green Bio-Organic Catalyst in Aqueous Medium

Abstract

A series of pyrano­[3,2-c]­quinolone derivatives has been synthesized in the presence of taurine (2-aminoethanesulfonic acid) as a green bio-organic catalyst and water as the solvent. The target compounds were synthesized through the three-component reaction between aldehydes, malononitrile/ethylcyanoacetate, and 4-hydroxy-1-methyl-2­(1H)-quinolone. The advantages of this protocol are excellent yields of products, short reaction times, cost efficiency, atom economy, and a simple work-up procedure with no need for extra purification techniques. Moreover, the catalyst can be easily recovered and reused for up to three cycles without losing any significant activity.

An Organocatalyzed Multicomponent Reaction: A Rapid and Efficient Practical Approach for 4H‐pyrano[3,2‐c]quinoline‐3‐carbonitriles Synthesis

“…[63] The 4H-pyrano[3,2-c]quinoline-3-carbonitriles synthesis reported by using different catalysts such as KF-Al 2 O 3 , [64] NH 4 OAc, [65] [BMIm]Cl, [66] BF 3 .SiO 2 , [67] diammonium hydrogen phosphate, [68] microwave, [69] EtOH : H 2 O, [70] Electrocatalytic using NaBr [71] and taurine. [72] In this context, the utility of versatile and convenient 4-hydroxy-quinoline-2-one precursor as substrate can afford synthetic method development using more efficient energy sources, less hazardous solvents and renewable and eco-friendly catalysts towards significant environmental and economic welfare. Accordingly, the continuous exploration of eco-friendly method for quinoline based scaffolds synthesis has attracted attention due to its promising pharmacological and industrial applications.…”