36747-96-3Relevant articles and documents
Oxidomolybdenum complexes for acid catalysis using alcohols as solvents and reactants
Gomes, Ana C.,Neves, Patrícia,Cunha-Silva, Luís,Valente, Anabela A.,Gon?alves, Isabel S.,Pillinger, Martyn
, p. 5207 - 5218 (2016)
The application field of dichloridodioxidomolybdenum(vi) chelate complexes, which have been intensively investigated as catalysts for liquid-phase olefin epoxidation, is broadened to encompass acid catalysis, in particular, alcoholysis and acetalisation reactions. Complex [MoO2Cl2(L)] (1) with L = 4,4′-di-tert-butyl-2,2′-bipyridine was chosen as (pre)catalyst. Depending on the reaction conditions, 1 either remained structurally intact or was transformed into different metal species, the structures of which were determined on the basis of single-crystal X-ray diffraction, spectroscopic techniques (FT-IR and 1H NMR), and elemental analysis. The first example of a mixed-ligand complex of the type [MoO2X(OR)(L)] (X = halide) is disclosed. This complex is one of only a handful of complexes known to date that exhibit an all-cis configuration instead of the usual cis-oxido, trans-X, cis-L configuration (X = anionic ligand). Mechanistic considerations of the formation of the metal species are made.
Polyoxometalate-modified reduced graphene oxide foam as a monolith reactor for efficient flow catalysis of epoxide ring-opening reactions
Jing, Xiaoting,Li, Zhen,Geng, Weijie,Lv, Hongjin,Chi, Yingnan,Hu, Changwen
, p. 8480 - 8488 (2021/04/12)
Continuous flow catalysis has been attracting significant interest due to its remarkable advantages over traditional batch reactions. In this work, a facile and broad-spectrum hydrothermal approach has been developed to construct polyoxometalate-modified reduced graphene oxide (POM@rGO) foam, which worked as a monolith reactor for efficient continuous flow catalysis of epoxide ring-opening reactions. The porous structures of rGO foam allow the high dispersion of the POM catalyst onto the substrate through electrostatic interactions. Specifically, a phosphotungstic acid (H3PW12O40, denoted as PW12)-modified rGO (PW12@rGO) monolith reactor exhibits remarkable catalytic activity and durability towards epoxide ring-opening reactions with alcohols, achieving 99% conversion and 92% selectivity for the methanolysis product in 10 min under ambient conditions without stirring. Notably, while coupling with a micro-injection pump, such PW12@rGO foam can work as an efficient continuous flow reactor towards methanolysis of styrene oxide for 38 h with 99% conversion and over 90% selectivity, reaching a turnover number (TON) as high as 28?044.
Cross-linked poly(N-vinylpyrrolidone)-titanium tetrachloride complex: A novel stable solid TiCl4 equivalent as a recyclable polymeric Lewis acid catalyst for regioselective ring-opening alcoholysis of epoxides
Rahmatpour, Ali,Sajjadinezhad, Seyed Mehrzad
, (2021/08/09)
Cross-linked poly(N-vinylpyrrolidone) resin beads were prepared as macromolecular ligand precursors by suspension copolymerization of N-vinyl-2-pyrrolidone and N,N′-methylenebisacrylamide (MBA) as a crosslinking agent in water. Subsequently, the resulting polymer carrier precursor was readily combined with titanium tetrachloride to form a stable polymeric coordination complex (PNVP/TiCl4), and this novel stable TiCl4 equivalent evaluated as a heterogeneous and reusable solid Lewis acid catalyst for the regio-and stereoselective nucleophilic ring opening of various epoxides with various alcohols to prepare β-alkoxy alcohols in excellent yields without generating any waste. The MBA-cross-linked PNVP and resultant catalyst were characterized by Fourier transform infrared spectroscopy (FT–IR), field-emission scanning electron microscope (FE–SEM), energy dispersive X-ray (EDX), inductively coupled plasma (ICP), and thermogravimetric analysis (TGA) techniques. Moreover, the catalyst is very stable, easily separated, and reused at least five times without significant loss of activity. In terms of scope, yields, the amount of catalyst used, and reaction time, the PNVP-TiCl4 complex catalyst is an improvement over previously reported heterogeneous catalysts for ring opening of epoxides methods. Further, the experimental outcome revealed that using the copolymer beads as carriers with a high percentage of crosslinking and the high mesh size leads had an adverse effect on the reaction rate.
Ship-in-bottle preparation of multi-SO3H functionalized ionic liquid@MIL-100(Fe) for acid-catalyzed ring-opening of epoxides
Mortazavi, Saeideh-Sadat,Masteri-Farahani, Majid,Abbasi, Alireza
, (2021/08/26)
The fact that the homogeneous acid catalysts are usually separated difficulty than heterogeneous catalysts from the reaction media, the opportunity to combine the advantages of both homogeneous and heterogeneous catalytic systems by immobilizing ILs within the pores of a porous solid support host is an alternative method. In this research, a multi-SO3H functionalized ionic liquid derived from hexamethylenetetramine (HMTA) and 1,3-propane sultone was entrapped inside the pores of MIL-100(Fe) through the ship-in-bottle method and utilized for heterogeneous acid-catalyzed ring-opening of epoxides under solvent-free conditions. The physicochemical properties of prepared catalyst were fully elucidated by various methods. FT-IR spectroscopy and elemental analysis approved the successful incorporation of modified groups within the MIL-100(Fe) cavities. The concentration of acid sites was measured via the acid–base titration which exhibited the 0.9?mmol/g H+ in the catalyst structure. Also, thermogravimetric analysis (TGA) profile showed the loosing of modified groups at 300–600°C. Moreover, X-ray diffraction (XRD) analysis showed that the MIL-100(Fe) structure was retained after modification and nitrogen adsorption–desorption analysis (BET method) manifested the decrease in surface area caused by incorporation of ionic liquid. The fabricated catalyst exhibited high catalytic efficiency in methanolysis of styrene oxide (99% conversion in 3?h) under ambient conditions and used without a substantial drop in product yield in further rounds.
