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Hydrogen-bond donating (HBD) organocatalysts have been employed as an important class of catalysts for the activation of small molecules. However, the use of these catalysts was restricted on account of the self-aggregation of HBD-active species. In this work, a successful approach was developed to construct novel urea–pyridine bridged periodic mesoporous organosilica (PMO) to prevent the unwanted self-recognition and aggregation of urea-based catalytic center by spatial isolation, unleashing its HBD organocatalytic activity along with cooperative effect from the pyridine unit for efficient Henry reaction. The urea–pyridine bridged PMO catalyst presents high structural stability and high catalytic recyclability. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Highly efficient and recyclable heterogeneous organocatalysts containing acidic functional groups such as 一CO2H and 一SO3H have been synthesized by post-synthesis modification of 2D-hexagonal mesoporous silica materials SBA-15 and MCM-41, respectively. The CO2H functionalized material is obtained via Schiff-base condensation of 3-aminopropyl grafted SBA-15 with 4-formylbenzoic acid, whereas 一SO3H functionalized material is prepared via partial oxidation of 3-mercaptopropyl grafted MCM-41 with dilute aqueous H2O2. These functionalized mesoporous materials have been thoroughly characterized by powder X-ray diffraction (PXRD), nitrogen adsorption/desorption studies, transmission electron microscopy (TEM) and UV visible diffuse reflectance spectroscopy. Both these materials have highly ordered 2D-hexagonal mesoporous structures with high surface areas and well-defined pore sizes. These acid functionalized materials have been used as heterogeneous catalysts for the condensation of aromatic aldehydes with 2-napthol under mild conditions in the presence or absence of a solvent affording high yields of the value added xanthenes. [ABSTRACT FROM AUTHOR]

Abstract: A new palladium grafted mesoporous organic polymer catalyst has been synthesized through the reaction of palladium(II) acetate with mesoporous poly-triallylamine (MPTA-1) in methanol. Powder XRD, HR TEM, FE SEM-EDS, AAS, UV–vis spectroscopic tools are employed to characterize this supported palladium catalyst Pd–MPTA-1. The Heck coupling reactions between a series of aryl halides and alkenes have afforded the corresponding C–C coupling products in good yield over this Pd-catalyst using water as reaction medium. This protocol provides a simple strategy for the generation of a variety of new C–C bonds by using this recyclable heterogeneous catalyst under environmentally benign conditions. [Copyright &y& Elsevier]

A new functionalized mesoporous polymer (MPTAT-1) has been synthesized viaorganic–organic radical polymerization of 2,4,6-triallyloxy-1,3,5-triazine (TAT) in aqueous medium in the presence of an anionic surfactant (sodium dodecyl sulfate) as template. Powder XRD and TEM image analysis suggests the presence of ordered 2D-hexagonal arrangement of pores in the material. N2sorption analysis reveals a moderately good surface area 135 m2g−1for this mesoporous polymer. The template free MPTAT-1 acts as an excellent support for immobilizing Pd(ii) at its surface and the resulting material showed very good catalytic activity in several C–C cross-coupling reactions like Mizoroki–Heck, Sonogashira and Suzuki–Miyaura in an environmentally benign reaction medium, water. The catalyst exhibits very high catalytic activity for the coupling of various aryl halides including aryl chlorides with alkenes or alkynes and the sodium salt of (trihydroxy)phenylborate. Due to strong binding with the functional groups of the polymer, the anchored Pd(ii) could not leach out from the surface of the mesoporous catalyst during the reaction and it has been reused several times without appreciable loss in catalytic activity. [ABSTRACT FROM AUTHOR]

Abstract: Knoevenagel condensation and [4+2] cycloaddition reactions are very important class of reactions in synthetic organic chemistry. We have prepared amino-functionalized mesoporous silica through co-condensation of 3-aminopropyltriethoxy-silane (APTES) along with tetraethylorthosilicate (TEOS) in presence of a cationic surfactant CTAB hydrothermally. Small angle powder XRD, HR TEM, FE SEM, N2 sorption and FT IR spectroscopic tools are used to characterize the 2D-hexagonal mesostructure and to identify the presence of surface –NH2 groups in amino-functionalized mesoporous silica material. Our experimental results reveal that amino-functionalized mesoporous silica is an efficient base catalyst for the Knoevenagel condensation of different aromatic aldehydes with malononitrile to α,β-unsaturated dicyanides under very mild reaction condition and in the presence of ethanol solvent. The isolated α,β-unsaturated dicyanides obtained through the condensation reaction further react very efficiently with cyclopentadiene to form a series of Diels–Alder cycloaddition products in excellent yields in the absence of any catalyst. [ABSTRACT FROM AUTHOR]