Multicomponent Synthesis of Structurally Diverse Spiroheterocycles using Bio-organic Catalyst in Aqueous Medium

Abstract

MCRs are one of the most significant tools in the synthesis of organic compounds. MCR is a rapid chemical technique that uses three or more reactants to produce products that sustain all structural and substructural properties of the initial components. MCRs are useful in all fields of synthetic chemistry because of their rapid rate of reaction, simple procedure and excellent yields. We reported an efficient and environmentally friendly domino approach for the synthesis of spiroheterocycles spiro annulated with indeno[1,2-b]quinoline. The spirooxindole scaffold has a significant structural role in several bioactive organic substances and pharmaceuticals like spirotryprostatin A and B, coerulescine, pteropodine horsfiline, alstonisine, elacomine, and rhynchophylline.5 Spiro heterocycle molecules, which have two rings that share a sp3 carbon atom, are key frameworks in pharmaceutical chemistry. They can be found in a wide range of both organic and synthetic materials as well as have several properties because of the rigidity and complexity of their structural design. Furthermore, spiroxindole is used as a key component in numerous medicines such as anticancer, antibacterial, antiviral, and inhibitors of the human NK-1 receptor The spiroheterocycles with privileged heterocyclic substructures have been synthesized using taurine (2-aminoethanesulfonic acid) as a green, sustainable, bio-organic and recyclable catalyst in a three-component reaction of isatins, 1,3-diketones, and 1-napthylamine in aqueous media. The present synthetic method is probably the first report to synthesize spiroheterocycles, spiroannulated with indeno[1,2-b]quinoline. Furthermore, the approach is valuable because of the excellent yield that results from the reaction in 15-20 min. The optimization of reaction conditions is an important case of efficient synthesis. The solvent, temperature, time and catalyst loading were all examined. The reusability of the catalyst was also investigated experimentally. The used catalyst taurine has a high activity as well as good reusability. The present synthetic protocol will be extended to synthesise a library of hybrid compounds. The present synthetic approach is cost-effective, and time-efficient with an easy-workup methodology that gives outstanding yields (80–95%) in 15–20 min. Taurine-catalyzed multicomponent reaction is a novel and efficient method for the synthesis of spiroannulated indeno[1,2-b]quinolines. The high catalytic activity of taurine as a catalyst with water as a green solvent makes the process environmentally friendly. The special features of the synthetic protocol include synthetic efficiency, operational simplicity, and reusability of the catalyst and it is expected to make significant contributions not only to drug discovery studies but also to pharmaceutical and therapeutic chemistry in view of introducing molecular diversity in the synthesized molecules. The current synthetic technique has various distinct characteristics, including simple procedure, high atom economy, mild reaction conditions and significant synthetic efficiency. The current synthesis method has been proposed to have contributed to the first report on the synthesis of spiroheterocycles with such a novel combination of preferred heterocycles employing taurine as a green bio-organic, reusable and easily recyclable catalyst. The benefits of this method include beneficial conditions in the environment, excellent purity that may be achieved without the need for column chromatography, and a reusable catalyst.