Abstract:Recent developments in Pd(0)- and Pd(ii)-catalysed alkenylation reactions for the synthesis of quinolines focusing on mechanistic understanding.
“…In the next step, the surface of Fe 3 O 4 @SiO 2 core/shell MNPs was functionalized with vinyl groups, by using trimethoxy vinylsilane (TMVS) 49 . In the final stage, the produced Fe 3 O 4 @SiO 2 @vinyl MNPs entered into a reaction with 2-aminothiazole in the presence of palladium (II) chloride, which leads to a Diels–Alder reaction on the surface of MNPs 50 . Figure 1 Schematic presentation of preparation route of Fe 3 O 4 @SiO 2 /TABHA catalytic system via Diels–Alder reaction approach.…”
In this study, a heterogeneous nanocatalyst is presented that is capable to efficiently catalyze the synthetic reactions of amide bond formation between the amino acids. This nanocatalyst which is named Fe3O4@SiO2/TABHA (TABHA stands for thio-aza-bicyclo-hepten amine), was composed of several layers that increased the surface area to be functionalized with 2-aminothiazole rings via Diels–Alder approach. Firstly, various analytic methods such as Fourier-transform infrared (FTIR) and energy-dispersive X-ray (EDX) spectroscopic methods, thermogravimetric analysis (TGA), electron microscopy (EM), and UV–vis diffuse reflectance spectroscopy (UV-DRS) have been used to characterize the desired structure of the Fe3O4@SiO2/TABHA catalyst. Afterward, the application of the presented catalytic system has been studied in the peptide bond formation reactions. Due to the existence of a magnetic core in the structure of the nanocatalyst, the nanoparticles (NPs) could be easily separated from the reaction medium by an external magnet. This special feature has been corroborated by the obtained results from vibrating-sample magnetometer (VSM) analysis that showed 24 emu g−1 magnetic saturation for the catalytic system. Amazingly, a small amount of Fe3O4@SiO2/TABHA particles (0.2 g) has resulted in ca. 90% efficiency in catalyzing the peptide bond formation at ambient temperature, over 4 h. Also, this nanocatalyst has demonstrated an acceptable recycling ability, where ca. 76% catalytic performance has been observed after four recycles. Due to high convenience in the preparation, application, and recyclization processes, and also because of lower cost than the traditional coupling reagents (like TBTU), the presented catalytic system is recommended for the industrial utilization.
“…In the next step, the surface of Fe 3 O 4 @SiO 2 core/shell MNPs was functionalized with vinyl groups, by using trimethoxy vinylsilane (TMVS) 49 . In the final stage, the produced Fe 3 O 4 @SiO 2 @vinyl MNPs entered into a reaction with 2-aminothiazole in the presence of palladium (II) chloride, which leads to a Diels–Alder reaction on the surface of MNPs 50 . Figure 1 Schematic presentation of preparation route of Fe 3 O 4 @SiO 2 /TABHA catalytic system via Diels–Alder reaction approach.…”
In this study, a heterogeneous nanocatalyst is presented that is capable to efficiently catalyze the synthetic reactions of amide bond formation between the amino acids. This nanocatalyst which is named Fe3O4@SiO2/TABHA (TABHA stands for thio-aza-bicyclo-hepten amine), was composed of several layers that increased the surface area to be functionalized with 2-aminothiazole rings via Diels–Alder approach. Firstly, various analytic methods such as Fourier-transform infrared (FTIR) and energy-dispersive X-ray (EDX) spectroscopic methods, thermogravimetric analysis (TGA), electron microscopy (EM), and UV–vis diffuse reflectance spectroscopy (UV-DRS) have been used to characterize the desired structure of the Fe3O4@SiO2/TABHA catalyst. Afterward, the application of the presented catalytic system has been studied in the peptide bond formation reactions. Due to the existence of a magnetic core in the structure of the nanocatalyst, the nanoparticles (NPs) could be easily separated from the reaction medium by an external magnet. This special feature has been corroborated by the obtained results from vibrating-sample magnetometer (VSM) analysis that showed 24 emu g−1 magnetic saturation for the catalytic system. Amazingly, a small amount of Fe3O4@SiO2/TABHA particles (0.2 g) has resulted in ca. 90% efficiency in catalyzing the peptide bond formation at ambient temperature, over 4 h. Also, this nanocatalyst has demonstrated an acceptable recycling ability, where ca. 76% catalytic performance has been observed after four recycles. Due to high convenience in the preparation, application, and recyclization processes, and also because of lower cost than the traditional coupling reagents (like TBTU), the presented catalytic system is recommended for the industrial utilization.
“…Therefore, the reduction of Pd(II) in the catalyst 1 to its activated form, Pd(0), occurs smoothly in DMF and CH 3 CN as oxidizable solvents. [115][116][117] Hence, oxidative addition of the Pd(0) species to aryl halide 3a-e affords…”
Section: The Proposed Mechanism For the Synthesis Of Cinnamic Acid De...mentioning
In this research, a novel supramolecular Pd(II) catalyst supported on chitosan grafted by L-asparagine and an EDTA linker, named Pd@ASP-EDTA-CS, was prepared for the first time. The structure of the...
“…A simple structure would be 1,1,3,3tetramethylguanidine 1 (TMG) (Figure 1), but also a variety of acyclic 2 (Barton's bases), cyclic 3 or bicyclic analogues 5-6, such as 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (hpp), also known as triazabicyclodecene (TBD) 6a have been widely studied. For example, as part of our program to develop new synthetic methods for heterocyclic systems, [9][10][11][12] we have prepared several cyclic guanidines, 2-aminoimidazoles of general structure 4, 13 whose framework can be found in biologically active natural products. Monoguanidines can present various coordination modes with the metal center, so their complexes with transition metals (e.g.…”
Section: Monoguanidines As Ligands In Metal-catalyzed Reactionsmentioning
Guanidines have received great attention due to their application as superbasic proton sponges and organocatalysts, as well as excellent N-donor ligands able to coordinate with different metals. The introduction of different substituents can modulate the basicity/nucleophilicity of the guanidines, their coordination ability, and thus, the electronic and steric properties of their metal complexes, regulating their catalytic activity. This review presents recent developments on guanidine-based ligand families [monoguanidine, bis(guanidine) and hybrid guanidine ligands], highlighting their potential in transition metalcatalyzed reactions.
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