Efficient and environmentally sustainable domino protocol for the synthesis of diversified spiroheterocycles with privileged heterocyclic substructures using bio-organic catalyst in aqueous medium

An efficient and environmentally sustainable synthetic protocol has been presented to synthesize structurally diverse spiroxindoles spiroannulated with indenopyrroloimidazoles, pyranopyrroloimidazoles, chromenopyrroloimidazoles, and imidazopyrrolopyrimidines involving three-component reaction of isatins, hydantoin, and beta-diketones in the presence of green and sustainable bio-organic catalyst, beta-amino acid, 2-aminoethanesulfonic acid (taurine), in aqueous media. The synthetic efficiency, operational simplicity, and reusability of catalyst make the present synthetic protocol cost effective, time efficient, and eco-friendly to synthesize molecules with structural diversity and molecular complexity and expected to contribute significantly not only to drug discovery research but also to pharmaceutical and medicinal chemistry.