Clean chemical synthesis of 2-amino-chromenes in water catalyzed by nanostructured diphosphate Na2CaP2O7

Efficient tandem synthesis of a variety of pyran-annulated heterocycles, 3,4-disubstituted isoxazol-5(4H)-ones, and α,β-unsaturated nitriles catalyzed by potassium hydrogen phthalate in water

“…Several synthetic methods have been widely applied for synthesis of pyran-based heterocyclic compounds, using many homogeneous or heterogeneous organic, inorganic, and nanomaterial catalysts, for example hexamethylenetetramine (HMT) [40], heteropolyacid [41], diammonium hydrogen phosphate [42], DBU [43], piperidine [44][45][46][47], tetrabutylammonium bromide (TBAB) [48], ionic liquids [49], morpholine [50], 4-(dimethylamino)pyridine (DMAP) [51], urea [52], 3-hydroxypropanaminium acetate (HPAA) [53], N-propylpiperazine sodium n-propionate (SBPPSP) [54], silica gel [55], sulfonic acid-functionalized silica [ [60], meglumine [61], I 2 /K 2 CO 3 [62], cetyltrimethylammonium bromide (CTABr) [63], nano-sized MgO [64], nano-structured Na 2 CaP 2 O 7 [65], NaHCO 3 [66], Na 2 CO 3 [67], triazine-functionalized ordered mesoporous organosilica [68], potassium phosphate tribasic trihydrate [69], Mg/Al hydrotalcite [70], Amberlyst A21 [71], DABCO [72], CeO 2 /CaO nanocomposite oxide [73], triton B [74], tetrabutylammonium chloride (TBAC) [75], nano-eggshell powder [76], basic alumina [77], [bmim]OH [78,79], LiBr [80], glycine [81], silica nanoparticles [82], ionic liquid choline chlorid...…”

SiO2–OSO3H Nanoparticles: An Efficient, Versatile and New Reagent for the One-Pot Synthesis of 2-Amino-8-Oxo-4,8-Dihydropyrano[3,2-b]Pyran-3-Carbonitrile Derivatives in Water, a Green Protocol

“…There was no reaction without nano-silica sulfuric acid in H 2 O under reflux ( Table 1, entry 1). The transformation of benzaldehyde with malononitrile and kojic acid proceeded smoothly with nano-silica sulfuric acid (0.006 g) in H 2 O (5 mL), and at the end of the reaction (about 15 min later), the product was collected by filtration and recrystallised from ethanol, affording the nicely crystalline 4a in good yield (95%, [3][4][5][6][7][8]. Different solvents, for example, CH 2 Cl 2 , EtOH, CH 3 CN and DMF were tested in the presence of nano-silica sulfuric acid as the catalyst, but unfortunately they resulted in low yields or no reaction (Table 1, entries 9-13).…”

Green Synthetic Approaches for Biologically Relevant 2-amino-4H-pyrans and 2-amino-4H-pyran-Annulated Heterocycles in Aqueous Media∗

“…[80]. An alternative and environmentally benign three-component strategy involving aromatic aldehydes, malononitrile, and α-naphthol for the synthesis of a series of 2-amino-chromenes in water medium with high atom-economy and good yields was described by Solhy et al [82] using nanostructured diphosphate, Na 2 CaP 2 O 7 , as a basic catalyst (Scheme 3). Later on, Khurana and his group [81] synthesized such compounds from different aromatic aldehydes bearing electron-withdrawing (such as nitro or halide group) and electron-donating groups (such as hydroxyl or alkoxy group) using 10 mol% of 1,8-diazabicyclo [5.4.0]undec-7-ene (DBU) in aqueous medium under reflux with 80-96% yields (Scheme 3).…”