Mo(VI) Complexes Immobilized on SBA-15 as an Efficient Catalyst for 1-Octene Epoxidation

SBA-15 materials were functionalized through a post-synthetic methodology with molybdenum-Schiff bases to provide catalytic activity in epoxidation reactions. Thus, glycidoxypropyl functionalities were first attached to the surface of the mesostructured silica, followed by the reaction of the immobilized oxirane groups with 2-amino propyl pyridine. This reaction allowed the obtaining of (hydroxypropyl)-2-aminomethyl pyridine ligands, directly tethered to the surface of the mesoporous silica-based SBA-15, which resulted in excellent chelating ligands to immobilize dioxo molydenum species by a reaction with MoO2(acac)2. This investigation comprises a thorough characterization of the process for building the immobilized molybdenum-Schiff base complexes, as well as the use of the obtained materials in 1-octene oxidation in the presence of organic hydroperoxides. These materials displayed high intrinsic catalytic activity in the epoxidation of 1-octene with organic hydroperoxides under a wide variety of conditions, although both the reaction solvent as well as the nature of the organic hydroperoxide, exerted a dramatic influence on the catalytic activity of these heterogeneous oxidation catalysts. Thus, whereas nonpolar solvents provided good epoxide yields with high efficiency in the use of the oxidant, polar solvents depressed the catalytic activity of the supported Mo-Schiff bases. These results have been ascribed to the competition with the solvent, when polar, for binding to the metal sites, thus avoiding the formation of the hydroperoxo-metal cycle and the epoxidation of the olefin. The catalysts presented here show good reusability with low catalytic activity decay after the first reuse.

Application of Silica-Supported Alkylating Reagents in a One-Pot, Sequential Protocol to Diverse Benzoxathiazepine 1,1-Dioxides

Applications of silica-ROMP reagents in a one-pot, sequential protocol have been developed for the synthesis of a variety of diverse benzoxathiazepine 1,1-dioxides. This protocol includes sulfonylation, intramolecular SNAr, alkylation with silica-supported oligomeric benzyl (Si-OBPn) and triazole (Si-OTPn) phosphates, and intermolecular SNAr addition with a number of secondary amines in one-pot to afford a variety of unique benzoxathiazepine 1,1-dioxides sultams in good to excellent yields.

Synthesis of High-Load, Hybrid Silica-Immobilized Heterocyclic Benzyl Phosphate (Si-OHBP) and Triazolyl Phosphate (Si-OHTP) Alkylating Reagents

The development of new ROMP-derived silica-immobilized heterocyclic phosphate reagents and their application in purification-free protocols is reported. Grafting of norbornenyl norbornenyl-functionalized (Nb-tagged) silica particles with functionalized Nb-tagged heterocyclic phosphate monomers efficiently yield high-load, hybrid silica-immobilized oligomeric heterobenzyl phosphates (Si-OHBP) and heterotriazolyl phosphates (Si-OHTP) as efficient alkylation agents. Applications of these reagents for the diversification of N-, O-, and S-nucleophilic species, for efficient heterobenzylation and hetero(triazolyl)methylation have been validated.

Silica-Supported Oligomeric Benzyl Phosphate (Si-OBP) and Triazole Phosphate (Si-OTP) Alkylating Reagents

The syntheses of silica-supported oligomeric benzyl phosphates (Si-OBP(n)) and triazole phosphates (Si-OTP(n)) using ring-opening metathesis polymerization (ROMP) for use as efficient alkylating reagents is reported. Ease of synthesis and grafting onto the surface of norbornenyl-tagged (Nb-tagged) silica particles has been demonstrated for benzyl phosphate and triazole phosphate monomers. It is shown that these silica polymer hybrid reagents, Si-OBP(n) and Si-OTP(n), can be used to carry out alkylation reactions with an array of different nucleophiles to afford the corresponding benzylated and (triazolyl)methylated products in good yield and high purity.

Analysis of trivalent cation complexation to functionalized mesoporous silica using solid-state NMR spectroscopy

The first comprehensive study of Al(iii) and Sc(iii) interactions with a novel hybrid material, N-[5-(trimethoxysilyl)-2-aza-1-oxopentyl]caprolactam functionalized mesoporous silica, was conducted using solid-state NMR spectroscopy.

Organic-inorganic hybrid mesoporous polymers fabricated by using (CTA)2S2O8 as self-decomposed soft templates

Organic-inorganic hybrid mesoporous polymers were successfully synthesized by using a template-directed free radical polymerization technique in aqueous solution at 0-5 °C with oxidative complexes as self-decomposed soft templates. The oxidative complexes ((CTA)(2)S(2)O(8)), which were formed between anionic oxidant (S(2)O(8)(2-)) and cationic surfactant (cetyltrimethylammonium bromide, CTAB) at 0-5 °C, can be automatically decomposed due to the reduction of S(2)O(8)(2-). No additional treatment was needed to remove the templates. The reactive functional monomer, 3-(trimethoxysilyl)propyl methacrylate (TMSPMA), was used as main monomer. Styrene was used as the comonomer. With simultaneous free radical copolymerization of TMSPMA and styrene, condensation of methoxysilyl groups, and the self-decomposition of (CTA)(2)S(2)O(8), organic-inorganic hybrid mesoporous polymers were successfully obtained. The mesoporous structures and morphologies of the resultant hybrid mesoporous polymers were found to be strongly dependent on the feed amounts of TMSPMA and styrene. In the absence of styrene, the hybrid polymer PTMSPMA exhibited mesh-like bicontinuous structures with mesopores and high surface area (335 m(2)/g). With the incorporation of styrene, mesoporous nanoparticles were obtained. The surface areas of the mesoporous nanoparticles decreased with the increase of styrene contents. The adsorption capabilities of such mesoporous polymers for organic dye (Congo red) and protein (bovine serum albumin) were also studied.