Clean chlorination of silica surfaces by a single-site substitution approach

A chlorination method for the selective substitution of well-defined isolated silanol groups of the silica surface has been developed using the catalytic Appel reaction. Spectroscopic analysis, complemented by elemental microanalysis studies, reveals that a quantitative chlorination could be achieved with highly dehydroxylated silica materials that exclusively possess non-hydrogen bonded silanol groups. The employed method did not leave any carbon or phosphorus residue on the silica surface and can be regarded as a promising tool for the future functionalization of metal oxide surfaces.

Magnetic nanoparticles-supported tungstic acid (MNP-TA): an efficient magnetic recyclable catalyst for the one-pot synthesis of spirooxindoles in water

This paper reports the preparation, characterization and catalytic application of a novel, magnetically separable catalyst consisting of tungstic acid supported on silica coated magnetic nanoparticles.

Synthesis and characterization of novel nanosilica molybdic acid and its first catalytic application in the synthesis of new and known pyranocoumarins

Nanosilica molybdic acid as an effective and environmentally safe heterogeneous catalyst has been developed for the synthesis of pyranocoumarins.

An Unexpected Catalytic Synthesis of Novel and Known Bis(Pyrazolyl) Methanes by the use of α-aryl-N-phenyl Nitrones in Aqueous Media

Reaction of-aryl- N-phenyl nitrones with 3-methyl-1-phenyl-2-pyrazoline-5-one in the presence of a catalytic amount of silica tungstic acid in EtOH/H2O afforded, unexpectedly, high yields of bis(3-hydroxy-1-phenylpyrazolyl)-arylmethanes instead of the two possible 1,3-addition products. This is the first report of the synthesis of bis(3-hydroxy-1-phenylpyrazolyl)-arylmethanes via the reaction of nitrones and a pyrazolin-5-one. A possible mechanism for the process is suggested.

Tungstic acid functionalized mesoporous SBA-15: a novel heterogeneous catalyst for facile one-pot synthesis of 2-amino-4H-chromenes in aqueous medium

A new highly ordered mesoporous tungstic acid functionalized SBA-15, TAFMC-1 has been synthesized via post-synthesis modification of mesoporous SBA-15 with (3-chloropropyl) triethoxysilane followed by substitution reaction of chlorine atom of the 3-chloropropyl group by tungstic acid group under refluxing conditions in n-hexane. The tungstic acid functionalized mesoporous silica material has been characterized by using small angle powder X-ray diffraction, N2 sorption, HR-TEM, FE-SEM, FT-IR and solid state MAS NMR studies. TAFMC-1 catalyzes the facile one-pot catalytic three-component condensation reaction of resorcinol, aromatic aldehyde and malononitrile for the synthesis of a diverse range of 2-amino-4H-chromenes in aqueous medium. This heterogeneous catalyst can be recycled very efficiently for six consecutive reaction cycles without significant loss of catalytic activity.

Graphene oxide nanosheets as metal-free catalysts in the three-component reactions based on aryl glyoxals to generate novel pyranocoumarins

Graphene oxide (GO) was employed as an efficient and powerful catalyst in one-pot, three-component synthesis of new pyranocoumarins.

Graphene oxide nanosheets promoted regioselective and green synthesis of new dicoumarols

Graphene oxide (GO) was obtained by modified Hummers oxidation of graphite and used as a highly efficient, metal-free, non-oxidative, and recyclable catalyst to promote the condensation of 4-hydroxycoumarin and aryl glyoxals for synthesis of new dicoumarols.