Arylation of indoles using cyclohexanones dually-catalyzed by niobic acid and palladium-on-carbons

2020 ◽  
Vol 18 (20) ◽  
pp. 3898-3902 ◽  
Author(s):  
Kazuho Ban ◽  
Yuta Yamamoto ◽  
Hironao Sajiki ◽  
Yoshinari Sawama
Keyword(s):  
Niobic Acid

3-Arylindoles could be effectively constructed from indoles and cyclohexanones in the presence of the dual catalysts of N2O5/C and Pd/C.

Niobic Acid as a Recyclable Heterogeneous Catalyst for the Solvent-Free Synthesis of Substituted Benzimidazoles

2013 ◽  
Vol 1 (2) ◽  
pp. 136-144 ◽  
Author(s):  
Beatriz Vieira ◽  
Angelita Barcellos ◽  
Ricardo Schumacher ◽  
Eder Lenardao ◽  
Diego Alves
Keyword(s):  
Heterogeneous Catalyst ◽  
Solvent Free ◽  
Niobic Acid ◽  
Recyclable Heterogeneous Catalyst ◽  
Solvent Free Synthesis

scholarly journals Reactivity and Reusability of Mesoporous Alumina Nanoparticles Modified with Sulfuric Acid and Niobic Acid in the Alkylation of Resorcinol

2014 ◽  
Vol 4 (1) ◽  
Author(s):  
Zainab Ramli ◽  
Hadi Nur ◽  
Sheela Chandren
Keyword(s):  
Sulfuric Acid ◽  
High Surface ◽  
Mesoporous Alumina ◽  
Alumina Nanoparticles ◽  
Lewis Acidity ◽  
Methyl Tert Butyl Ether ◽  
Solid Catalyst ◽  
Brønsted Acidity ◽  
Brönsted Acidity ◽  
Niobic Acid

With the development of large molecule hydrocarbon processes, mesoporous alumina which possesses high surface area with narrow pore size distribution has received a great deal of attention. However, its acid properties lack Bronsted acidity and showed only Lewis acid sites, making it an inactive solid catalyst in the alkylation of resorcinol, a reaction which requires the usage of solid acid catalysts with both Bronsted and Lewis acidity. In this study, in order to introduce Bronsted acidity to mesoporous alumina, sulfuric acid (H2SO4) and niobic acid (Nb2O5.nH2O) are introduced to the alumina. The reactivity of mesoporous alumina nanoparticles (MAN), Nb2O5.nH2O/MAN and H2SO4/MAN were tested out on the alkylation of resorcinol with methyl tert-butyl ether. No product was obtained using pure MAN, while both H2SO4/MAN and Nb2O5.nH2O/MAN managed to produce butylated resorcinol. Mesoporous alumina nanoparticles incorporated with sulfuric acid produced a greater amount of dibutylated resorcinol, which theoretically is a better antioxidant compared to monobutylated resorcinol. The reusability of the H2SO4/MAN catalyst was also better as dibutylated product was still obtained even in the second use. This indicates that sulfuric acid has created a more stable and also higher strength of Bronsted acidity in alumina as compared to niobic acid.

Layered niobic acid with self-exfoliatable nanosheets and adjustable acidity for catalytic hydration of ethylene oxide

2011 ◽  
Vol 280 (2) ◽  
pp. 247-254 ◽  
Author(s):  
Zhi-Jian Yang ◽  
Ye-Fei Li ◽  
Qing-Bin Wu ◽  
Nan Ren ◽  
Ya-Hong Zhang ◽  
...  
Keyword(s):  
Ethylene Oxide ◽  
Niobic Acid

scholarly journals Impact of Thermal Treatment of Nb2O5 on Its Performance in Glucose Dehydration to 5-Hydroxymethylfurfural in Water

Nanomaterials ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1685
Author(s):  
Katarzyna Morawa Eblagon ◽  
Anna Malaika ◽  
Karolina Ptaszynska ◽  
Manuel Fernando R. Pereira ◽  
José Luís Figueiredo
Keyword(s):  
Thermal Treatment ◽  
Surface Area ◽  
Pure Water ◽  
High Surface ◽  
High Surface Area ◽  
Acid Sites ◽  
High Ratio ◽  
Total Acidity ◽  
One Pot ◽  
Niobic Acid

The cascade dehydration of glucose to 5-hydroxymethylfurfural (HMF) was carried out in water over a series of Nb2O5 catalysts, which were derived from the thermal treatment of niobic acid at 300 and 550 °C, under air or inert atmosphere. Amorphous niobic acid showed high surface area (366 m2/g) and large acidity (2.35 mmol/g). With increasing the temperature of the thermal treatment up to 550 °C, the amorphous Nb2O5 was gradually transformed into a pseudohexagonal phase, resulting in a decrease in surface area (27–39 m2/g) and total acidity (0.05–0.19 mmol/g). The catalysts’ performance in cascade dehydration of glucose realized in pure water was strongly influenced by the total acidity of these materials. A remarkable yield of 37% HMF in one-pot reaction in water was achieved using mesoporous amorphous niobium oxide prepared by thermal treatment of niobic acid at 300 °C in air. The best-performing catalyst displayed a total acidity lower than niobic acid (1.69 mmol/g) which afforded a correct balance between a high glucose conversion and limited further conversion of the target product to numerous polymers and humins. On the other hand, the treatment of niobic acid at 550 °C, independently of the atmosphere used during the sample preparation (i.e., air or N2), resulted in Nb2O5 catalysts with a high ratio of Lewis to Brønsted acid sites and poor total acidity. These materials excelled at catalyzing the isomerization step in the tandem process.

scholarly journals Facile Hydrogenative Deprotection of N-Benzyl Groups Using a Mixed Catalyst of Palladium and Niobic Acid-on-Carbon

ACS Omega ◽  
2020 ◽  
Vol 5 (6) ◽  
pp. 2699-2709 ◽  
Author(s):  
Yuta Yamamoto ◽  
Eisho Shimizu ◽  
Kazuho Ban ◽  
Yoshiyuki Wada ◽  
Tomoteru Mizusaki ◽  
...  
Keyword(s):  
Mixed Catalyst ◽  
Niobic Acid
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