Xanthenes and their analogues have been receiving attention owing to their biological activities. These include antiviral,1 anti-inflammatory2 and antiplasmodial properties.3 These heterocyclic molecules have also been widely used as pH sensitive fluorescent materials for visualization of luminescent dyes, laser technology biomolecules and sensitizers in photodynamic therapy. Some of the more well-known frameworks with biological properties are shown in Figure 1. To date, methods for the synthesis of xanthenes have been reported using multicompo-nent reactions (MCRs) in the presence of catalysts. Among the catalysts are eerie ammonium nitrate,12 [Hbim]BF4,13 strontium triflate,14 sulfonic acid functionalized LUS-1,15 Fe3O4@SiO2-SO3H,16 nano-alumina sulfuric acid,17 zinc oxide nanoparticles,18 NaHSO4-SiO2,19 trityl chloride,20 Fe3O4 nanoparticles,21 sulfonic acid-functionalized phtha-limide,22 sulfamic acid,23 boron sulphonic acid,24 trichloromelamine,25 [cmmim][BF4],26 NO2-Fe(III)Pc/C,27 diatomite-SO3H,28 phosphosulfonic acid,29 silica sulfuric acid,30 [H-NMP][HSO4],31 Mg(BF4)2 doped in [BMIm][BF4],32 [(n-propyl)2NH2][HSO4],33 SiO2-Pr-SO3H,34 AHS@MMT,35 wet cyanuric chloride,36 and 1,3-disulfonic acid imidazo-lium hydrogen sulfate.37 Notwithstanding the value of specific applications, some of these methods have limitations. Chief among these are long time reactions, low yields, the use of strongly acidic conditions, difficult work-up, and toxic and expensive catalysts. To address some of these concerns, we have recently reported on the use of glycine as a natural, bio-based and biodegradable catalyst.38 We now report on the use of glycine for the MCR preparation of xanthenes.
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