Browse
Submit Data
Databases
API
Help

Dataset Information

29 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Hf(OTf)4 as a Highly Potent Catalyst for the Synthesis of Mannich Bases under Solvent-Free Conditions.

ABSTRACT: Hf(OTf)4 was identified as a highly potent catalyst (0.1-0.5 mol%) for three-component Mannich reaction under solvent-free conditions. Hf(OTf)4-catalyzed Mannich reaction exhibited excellent regioselectivity and diastereoselectivity when alkyl ketones were employed as substrates. 1H NMR tracing of the H/D exchange reaction of ketones in MeOH-d4 indicated that Hf(OTf)4 could significantly promote the keto-enol tautomerization, thereby contributing to the acceleration of reaction rate.

SUBMITTER: Han SB

PROVIDER: S-EPMC7024362 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Hf(OTf)4 as a Highly Potent Catalyst for the Synthesis of Mannich Bases under Solvent-Free Conditions.

Han Shuai-Bo SB Wei Jing-Ying JY Peng Xiao-Chong XC Liu Rong R Gong Shan-Shan SS Sun Qi Q

Molecules (Basel, Switzerland) 20200117 2

Hf(OTf)4 was identified as a highly potent catalyst (0.1-0.5 mol%) for three-component Mannich reaction under solvent-free conditions. Hf(OTf)4-catalyzed Mannich reaction exhibited excellent regioselectivity and diastereoselectivity when alkyl ketones were employed as substrates. 1H NMR tracing of the H/D exchange reaction of ketones in MeOH-d4 indicated that Hf(OTf)4 could significantly promote the keto-enol tautomerization, thereby ...[more]

PMID: 31963465

Similar Datasets

One-pot multicomponent nitro-Mannich reaction using a heterogeneous catalyst under solvent-free conditions.

Project description:An environmentally-friendly, one-pot multicomponent reaction of various aldehydes, amines and nitroalkanes for the synthesis of ?-nitroamines is here described. Amberlyst A-21 supported CuI was found to be a highly efficient novel heterogeneous catalyst for the three-component nitro-Mannich reaction between aldehydes, amines and nitroalkanes. The developed protocol is performed in a solvent-free medium to produce a variety of ?-nitroamines in good to excellent yields within short reaction times. The catalyst can be easily prepared and recovered. It has been tested up to eight times with only a minor activity loss.

| S-EPMC6026460 | biostudies-literature

Highly Efficient Synthesis of Substituted 3,4-Dihydropyrimidin-2-(1H)-ones (DHPMs) Catalyzed by Hf(OTf)₄: Mechanistic Insights into Reaction Pathways under Metal Lewis Acid Catalysis and Solvent-Free Conditions.

Project description:In our studies on the catalytic activity of Group IVB transition metal Lewis acids, Hf(OTf)₄ was identified as a highly potent catalyst for "one-pot, three-component" Biginelli reaction. More importantly, it was found that solvent-free conditions, in contrast to solvent-based conditions, could dramatically promote the Hf(OTf)₄-catalyzed formation of 3,4-dihydro-pyrimidin-2-(1H)-ones. To provide a mechanistic explanation, we closely examined the catalytic effects of Hf(OTf)₄ on all three potential reaction pathways in both "sequential bimolecular condensations" and "one-pot, three-component" manners. The experimental results showed that the synergistic effects of solvent-free conditions and Hf(OTf)₄ catalysis not only drastically accelerate Biginelli reaction by enhancing the imine route and activating the enamine route but also avoid the formation of Knoevenagel adduct, which may lead to an undesired byproduct. In addition, ¹H-MMR tracing of the H-D exchange reaction of methyl acetoacetate in MeOH-d₄ indicated that Hf(IV) cation may significantly accelerate ketone-enol tautomerization and activate the β-ketone moiety, thereby contributing to the overall reaction rate.

| S-EPMC6359175 | biostudies-literature

Synthesis of Novel 1,4-Naphthoquinones Possessing Indole Scaffolds Using In(OTf)? in Solvent-Free Conditions.

Project description:Novel 1,4-naphthoquinones possessing indole scaffolds were prepared by the reaction of 2-hydroxy-1,4-naphthoquinone-substituted salicylic aldehydes and indoles using In(OTf)? as a catalyst. The method has the advantages of simple operation, mild reaction conditions, and friendly environment.

| S-EPMC6222671 | biostudies-literature

Modification of Cellulose with Succinic Anhydride in TBAA/DMSO Mixed Solvent under Catalyst-Free Conditions.

Project description:Homogeneous modification of cellulose with succinic anhydride was performed using tetrabutylammonium acetate (TBAA)/dimethyl sulfoxide (DMSO) mixed solvent. The molar ratio of succinic anhydride (SA) to free hydroxyl groups in the anhydroglucose units (AGU), TBAA dosage, reaction temperature, and reaction time were investigated. The highest degree of substitution (DS) value of 1.191 was obtained in a 10 wt% TBAA/DMSO mixed solvent at 60 °C for 60 min, and the molar ratio of SA/AGU was 6/1. The molar ratio of SA/AGU and the TBAA dosage showed a significant influence on the reaction. The succinoylated cellulose was characterized by ATR-FTIR, TGA, XRD, solid state CP/MAS 13C NMR spectroscopy (CP/MAS 13C NMR), and SEM. Moreover, the modified cellulose was applied for the adsorption of Cu2+ and Cd2+, and both the DS values of modified cellulose and pH of the heavy metal ion solutions affected the adsorption capacity of succinylated cellulose. The highest capacity for Cu2+ and Cd2+ adsorption was 42.05 mg/g and 49.0 mg/g, respectively.

| S-EPMC5459046 | biostudies-literature

Indolyl Azaspiroketal Mannich Bases Are Potent Antimycobacterial Agents with Selective Membrane Permeabilizing Effects and in Vivo Activity.

Project description:The inclusion of an azaspiroketal Mannich base in the membrane targeting antitubercular 6-methoxy-1- n-octyl-1 H-indole scaffold resulted in analogs with improved selectivity and submicromolar activity against Mycobacterium tuberculosis H37Rv. The potency enhancing properties of the spiro-fused ring motif was affirmed by SAR and validated in a mouse model of tuberculosis. As expected for membrane inserting agents, the indolyl azaspiroketal Mannich bases perturbed phospholipid vesicles, permeabilized bacterial cells, and induced the mycobacterial cell envelope stress reporter promoter p iniBAC. Surprisingly, their membrane disruptive effects did not appear to be associated with bacterial membrane depolarization. This profile was not uniquely associated with azaspiroketal Mannich bases but was characteristic of indolyl Mannich bases as a class. Whereas resistant mycobacteria could not be isolated for a less potent indolyl Mannich base, the more potent azaspiroketal analog displayed low spontaneous resistance mutation frequency of 10-8/CFU. This may indicate involvement of an additional envelope-related target in its mechanism of action.

| S-EPMC6043372 | biostudies-literature

Rapid and efficient synthesis of formamidines in a catalyst-free and solvent-free system.

Project description:An operationally rapid and efficient synthesis of N-sulfonyl formamidines that proceeds under mild conditions was achieved by reaction of a mixture of an amine, a sulfonyl azide, and a terminal ynone under catalyst-free and solvent-free conditions. Terminal ynones provide the C source to formamidines via complete cleavage of C[triple bond, length as m-dash]C.

| S-EPMC9042323 | biostudies-literature

Vegetable oil derived solvent, and catalyst free "click chemistry" thermoplastic polytriazoles.

Project description:Azide-alkyne Huisgen "click" chemistry provides new synthetic routes for making thermoplastic polytriazole polymers-without solvent or catalyst. This method was used to polymerize three diester dialkyne monomers with a lipid derived 18 carbon diazide to produce a series of polymers (labelled C18C18, C18C9, and C18C4 based on monomer chain lengths) free of residual solvent and catalyst. Three diester dialkyne monomers were synthesized with ester chain lengths of 4, 9, and 18 carbons from renewable sources. Significant differences in thermal and mechanical properties were observed between C18C9 and the two other polymers. C18C9 presented a lower melting temperature, higher elongation at break, and reduced Young's modulus compared to C18C4 and C18C18. This was due to the "odd-even" effect induced by the number of carbon atoms in the monomers which resulted in orientation of the ester linkages of C18C9 in the same direction, thereby reducing hydrogen bonding. The thermoplastic polytriazoles presented are novel polymers derived from vegetable oil with favourable mechanical and thermal properties suitable for a large range of applications where no residual solvent or catalyst can be tolerated. Their added potential biocompatibility and biodegradability make them ideal for applications in the medical and pharmaceutical industries.

| S-EPMC4085725 | biostudies-literature

Learning To Predict Reaction Conditions: Relationships between Solvent, Molecular Structure, and Catalyst.

Project description:Reaction databases provide a great deal of useful information to assist planning of experiments but do not provide any interpretation or chemical concepts to accompany this information. In this work, reactions are labeled with experimental conditions, and network analysis shows that consistencies within clusters of data points can be leveraged to organize this information. In particular, this analysis shows how particular experimental conditions (specifically solvent) are effective in enabling specific organic reactions (Friedel-Crafts, Aldol addition, Claisen condensation, Diels-Alder, and Wittig), including variations within each reaction class. Network analysis shows data points for reactions tend to break into clusters that depend on the catalyst and chemical structure. This type of clustering, which mimics how a chemist reasons, is derived directly from the network. Therefore, the findings of this work could augment synthesis planning by providing predictions in a fashion that mimics human chemists. To numerically evaluate solvent prediction ability, three methods are compared: network analysis (through the k-nearest neighbor algorithm), a support vector machine, and a deep neural network. The most accurate method in 4 of the 5 test cases is the network analysis, with deep neural networks also showing good prediction scores. The network analysis tool was evaluated by an expert panel of chemists, who generally agreed that the algorithm produced accurate solvent choices while simultaneously being transparent in the underlying reasons for its predictions.

| S-EPMC7167595 | biostudies-literature

Silica sulfuric acid: a reusable solid catalyst for one pot synthesis of densely substituted pyrrole-fused isocoumarins under solvent-free conditions.

Project description:A convenient and efficient methodology for the synthesis of densely substituted pyrrole-fused isocoumarins, which employs solid-supported silica sulfuric acid (SSA) as catalyst, has been developed. When the mixture of ninhydrin adducts of acetylacetone/ethyl acetoacetate and primary amines was heated on the solid surface of SSA under solvent-free conditions, the pyrrole-fused isocoumarins were formed in good yields. This synthetic method has several advantages such as the employment of solvent-free reaction conditions without the use of any toxic reagents and metal catalysts, the ease of product isolation, the use of a recyclable catalyst, the low cost, the easy availability of the starting materials, and the excellent yields of products.

| S-EPMC3869253 | biostudies-literature

Tunable microwave-assisted method for the solvent-free and catalyst-free peracetylation of natural products.

Project description:Background: The peracetylation is a simple chemical modification that can be used to enhance the bioavailability of hydrophilic products and to obtain safe and stable pro-drugs. Results: A totally green, solvent-free and catalyst-free microwave (MW)-assisted method for peracetylation of natural products such as oleuropein, alpha-hederin, quercetin and rutin is presented. By simply tuning the MW heating program, polyols with chemical diverse -OH groups or thermolabile functionalities can be peracetylated to improve the biological activity without degradation of the natural starting molecules. An evaluation of the process greenness was performed. Conclusion: The method is potentially universally applicable for green acetylation of hydrophilic biological molecules, potentially easily scalable for industrial applications, including pharmaceutical, cosmetic and food industry.

| S-EPMC5082547 | biostudies-literature