Immobilized Lanthanum(III) Triflate on Graphene Oxide as a New Multifunctional Heterogeneous Catalyst for the One-Pot Five-Component Synthesis of Bis(pyrazolyl)methanes

Abstract

In this work, immobilized lanthanum­(III) triflate on graphene oxide as a new multifunctional heterogeneous catalyst has been synthesized. The structure of immobilized lanthanum­(III) triflate on amine-grafted graphene oxide [La­(OTf)2-grafted-GO] was established by FT-IR, XPS, and solid-state 13C MAS NMR. The morphology and distribution of elements on La­(OTf)2-grafted-GO was determined by FESEM, TEM, and EDS images. La­(OTf)2-grafted-GO was tested as the first reusable (Lewis and Brønsted) acid–base multifunctional catalyst for the efficient one-pot five-component synthesis of bis­(pyrazolyl)­methanes. This multifunctional catalyst exhibits a high synergic effect in this one-pot tandem reaction. Due to the uniform spreading of the active sites along with the crumpling structure of the catalyst, reactants and products can simply move toward the catalytic active sites on the surfaces of the catalyst without significant mass-transfer limitation. These properties increase the catalytic activity of La­(OTf)2-grafted-GO. Moreover, the catalyst was readily recycled and reused 9 times. The morphology and structure of La­(OTf)2-grafted-GO remained intact after 9 recoveries according to the FT-IR spectrum and TEM image of the used catalyst.

Amino-polystyrene supported hexaethylene glycol-bridged ionic liquid as an efficient heterogeneous catalyst for water-mediated nucleophilic hydroxylation

“…1 The sustainability of green chemistry depends on; (i) the use of multicomponent reactions, solvent-free conditions, or benign solvents, (ii) the discovery of promising, less toxic reagents and catalytic systems, (iii) the design of reliable and cost-effective methodologies, and (iv) the use of renewable resources, energy efficient catalytic processes, and the further development of separation procedures. 2,3 With these objectives in mind, considerable interest has been focused on ionic liquids (ILs) during the past decade because they can provide efficient media and catalysts for organic reactions (Fig. 1).…”

Integrated Process for the Production of Lactic Acid from Lignocellulosic Biomass: From Biomass Fractionation and Characterization to Chemocatalytic Conversion with Lanthanum(III) Triflate

“…Although the use of La­(OTf) 3 to convert biomass-derived carbohydrates into lactic acid was successfully realized in aqueous media, several technical issues associated with a homogeneous catalyst arose in downstream processing. Thus, there have been efforts to immobilize La­(OTf) 3 on solid supports to improve the recyclability and reusability of the catalyst, , which is highly desirable in downstream processes. In this work, the immobilization of La­(OTf) 3 onto silica followed by catalytic conversion into lactic acid was attempted to examine the catalyst recyclability.…”

Recent Developments on Five-Component Reactions

“…A common method for the synthesis of 4,4′-(arylmethylene)bis(1 H -pyrazol-5-ol) derivatives is to conduct a pseudo-5CR of two equiv each of phenylhydrazines and ethyl acetoacetate with one equiv of aromatic aldehydes through a cycloaddition-Knoevenagel-Michael reaction sequence. In recent years, the synthesis of bis(1 H -pyrazol-5-ols) has been accomplished using different catalysts, such as nanocatalyst Pd(0)-guanidine@MCM-41 [ 34 ], guanidine hydrochloride [ 35 ], α -Casein [ 36 ], ZnAl 2 O 4 nanoparticle [ 37 ], La(OTf) 2 -grafted-GO (graphene oxide) [ 38 ], amino acid-based ionic liquids (AAILs) [ 39 ], and CuCr 2 O 4 nanoparticle [ 40 ]. Catalyst-free conditions have also been reported [ 41 ].…”