scholarly journals Acid-catalyzed rearrangements in arenes: interconversions in the quaterphenyl series

2019 ◽  
Vol 15 ◽  
pp. 2655-2663
Author(s):  
Sarah L Skraba-Joiner ◽  
Carter J Holt ◽  
Richard P Johnson
Keyword(s):  
Complex Network ◽  
High Field ◽  
Product Formation ◽  
Nmr Analysis ◽  
Thermodynamic Control ◽  
Implicit Solvation ◽  
Reaction Conditions ◽  
Microwave Reactor ◽  
Acid Catalyzed ◽  
Sole Product

Arenes undergo rearrangement of phenyl, alkyl, halogen and other groups through the intermediacy of ipso arenium ions in which a proton is attached at the same carbon as the migrating substituent. Interconversions among the six quaterphenyl isomers have been studied here as a model for rearrangements of linear polyphenyls. All reactions were carried out in 1 M CF3SO3H (TfOH) in dichloroethane at 150 °C in a microwave reactor for 30–60 min, with product formation assessed by high field NMR analysis. Under these reaction conditions, m,p'-quaterphenyl is the equilibrium product. This isomer is unchanged by the reaction conditions and all other quaterphenyl isomers rearrange to m,p' as the dominant or sole product. DFT computations with inclusion of implicit solvation support a complex network of phenyl and biphenyl shifts, with barriers to rearrangement in the range of 10–21 kcal/mol. Consistent with experiments, the lowest energy arenium ion located on this surface is due to protonation of m,p'-quaterphenyl. This supports thermodynamic control based on carbocation energies.

Notizen: High Pressure Reactions, I Evidence for Two Concurrent Mechanisms in Lewis-Acid Catalyzed Alkylation of Aromatics with Olefins

1976 ◽  
Vol 31 (2) ◽  
pp. 277-278 ◽  
Author(s):  
H. Tiltscher ◽  
R. Lohmüller
Keyword(s):  
High Pressure ◽  
Pressure Range ◽  
Reaction Rate ◽  
Initial Reaction Rate ◽  
Product Formation ◽  
Initial Reaction ◽  
Homogeneous Reaction ◽  
Reaction Conditions ◽  
Alkylation Of Benzene ◽  
Acid Catalyzed

A kinetic study was made of the primary step of the alkylation of benzene with propylene and ferric chloride as catalyst under homogeneous reaction conditions at several pressures up to 2 kbar. Initial reaction rate of cumene formation shows a minimum in the medium pressure range, thus indicating that product formation occurs via two different reaction paths with opposite pressure dependence.

scholarly journals Bio-Waste Curd Water as a Greener Protocol for the Synthesis of Biginelli Products at Ambient Temperature

2021 ◽  
Vol 5 (2) ◽  
Keyword(s):  
Waste Water ◽  
Biginelli Reaction ◽  
Product Formation ◽  
Green Solvent ◽  
Reaction Conditions ◽  
Short Reaction Time ◽  
Acid Catalyzed ◽  
Catalyzed Reactions ◽  
Continuous Product ◽  
Successive Method

A highly efficient, greener and reusable protocol has been developed for the Biginelli reaction. The biowaste curd water employed as a green solvent as well as catalyst for the synthesis of dihydropyrimidinones derivatives. The soluble organic acid (i.e. lactic acid) responsible for the acidity to curd water which adequately fulfills the purpose of acid catalyzed reaction, where three component coupling of aldehyde, urea and ethyl acetoacetate reacted together in the presence of curd water at a low temperature and yields classical dihydropyrimidinones derivatives. During the reaction, continuous product formation and isolation was observed. The product precipitate was separated by the successive method of filtration. This bio-waste water catalyzed method is highly retrievable and advantageous over the trend of high-temperature Bronsted acid/metal acid catalyzed reactions offering the product. Compared with the classical Biginelli reaction conditions, this new method has the advantage of good yields (76-82%) and short reaction time (2-3 hours)

Naturally Occurring Organic Acid-catalyzed Facile Diastereoselective Synthesis of Biologically Active (E)-3-(arylimino)indolin-2-one Derivatives in Water at Room Temperature

2019 ◽  
Vol 23 (16) ◽  
pp. 1778-1788 ◽  
Author(s):  
Gurpreet Kaur ◽  
Arvind Singh ◽  
Kiran Bala ◽  
Mamta Devi ◽  
Anjana Kumari ◽  
...  
Keyword(s):  
Room Temperature ◽  
Biologically Active ◽  
Environmentally Benign ◽  
Diastereoselective Synthesis ◽  
Substituted Anilines ◽  
Reaction Conditions ◽  
Naturally Occurring ◽  
Acid Catalyzed ◽  
Reaction Media ◽  
Column Chromatographic

A simple, straightforward and efficient method has been developed for the synthesis of (E)-3-(arylimino)indolin-2-one derivatives and (E)-2-((4-methoxyphenyl)imino)- acenaphthylen-1(2H)-one. The synthesis of these biologically-significant scaffolds was achieved from the reactions of various substituted anilines and isatins or acenaphthaquinone, respectively, using commercially available, environmentally benign and naturally occurring organic acids such as mandelic acid or itaconic acid as catalyst in aqueous medium at room temperature. Mild reaction conditions, energy efficiency, good to excellent yields, environmentally benign conditions, easy isolation of products, no need of column chromatographic separation and the reusability of reaction media are some of the significant features of the present protocol.

Bu4N+-Controlled Addition and Olefination with Ethyl 2-(Trimethylsilyl)acetate via Silicon Activation

Synlett ◽  
2017 ◽  
Vol 28 (18) ◽  
pp. 2401-2406 ◽  
Author(s):  
Donal O’Shea ◽  
Manas Das ◽  
Atul Manvar ◽  
Ian Fox ◽  
Dilwyn Roberts
Keyword(s):  
Room Temperature ◽  
Product Formation ◽  
Unsaturated Ester ◽  
Reaction Conditions ◽  
Diverse Range ◽  
Inorganic Cation ◽  
Tetrabutyl Ammonium ◽  
Aldehydes And Ketones ◽  
Subsequent Elimination ◽  
Hydroxy Esters

Catalytic Bu4NOAc as silicon activator of ethyl 2-(trimethylsilyl)acetate, in THF, was utilized for the synthesis of β-hydroxy esters, whereas employing catalytic Bu4NOTMS gave α,β-unsaturated esters. The established reaction conditions were applicable to a diverse range of aromatic, heteroaromatic, aliphatic aldehydes and ketones. Reactions were achieved at room temperature without taking any of the specialized precautions that are in place for other organometallics. A stepwise olefination pathway via silylated β-hydroxy esters with subsequent elimination to form the α,β-unsaturated ester has been demonstrated. The key to selective product formation lies in use of the weaker acetate activator which suppresses subsequent elimination whereas stronger TMSO– activator (and base) facilitates both addition and elimination steps. The use of tetrabutyl ammonium salts for both acetate and trimethylsilyloxide activators provide enhanced silicon activation when compared to their inorganic cation counterparts.

1H-NMR Analysis of Degree of Substitution in N,O-Carboxymethyl Chitosans from Various Chitosan Sources and Types

2012 ◽  
Vol 506 ◽  
pp. 158-161 ◽  
Author(s):  
A. Jaidee ◽  
Pornchai Rachtanapun ◽  
S. Luangkamin
Keyword(s):  
Chemical Structure ◽  
Carboxymethyl Chitosan ◽  
Degree Of Substitution ◽  
Resonance Spectroscopy ◽  
Nmr Analysis ◽  
Reaction Conditions ◽  
H Nmr ◽  
Fourier Transformed Infrared Spectroscopy ◽  
Chitosan Oligomer ◽  
Ft Ir

N,O-Carboxymethyl chitosans were synthesized by the reaction between shrimp, crab and squid chitosans with monochloroacetic acid under basic conditions at 50°C. The mole ratio of reactants was obtained from various reaction conditions of shrimp chitosan polymer and oligomer types. The mole ratio 1:12:6 of chitosan:sodium hydroxide:monochloroacetic acid was used for preparing carboxymethyl of chitosan polymer types while carboxymethyl of chitosan oligomer types were used the mole ratio 1:6:3 of chitosan:sodium hydroxide:monochloroacetic acid. The chemical structure was analyzed by fourier transformed infrared spectroscopy (FT-IR) and proton nuclear magnatic resonance spectroscopy (1H-NMR). The FT-IR was used for confirm the insertion of carboxymethyl group on chitosan molecules. The 1H-NMR was used for determining the degree of substitution (DS) of carboxymethylation at hydroxyl and amino sites of chitosans. Carboxymethyl chitosan samples had the total DS of carboxymethylation ranging from 1.0-2.2. The highest of DS of carboxymethylation was from shrimp chitosan oligomer type.

Synergistic effect of co-reactant promotes one-step oxidation of cyclohexane into adipic acid catalyzed by manganese porphyrins

2015 ◽  
Vol 93 (7) ◽  
pp. 696-701 ◽  
Author(s):  
Hui Li ◽  
Yuanbin She ◽  
Haiyan Fu ◽  
Meijuan Cao ◽  
Jing Wang ◽  
...  
Keyword(s):  
Synergistic Effect ◽  
Co Oxidation ◽  
Adipic Acid ◽  
Molar Ratio ◽  
Reaction Conditions ◽  
Catalyst Structure ◽  
Manganese Porphyrins ◽  
Co Oxidation Reaction ◽  
One Step ◽  
Acid Catalyzed

The synergistic effect of cyclohexane and cyclohexanone promoted synthesis of adipic acid catalyzed by [MnIIIT(p-Cl)PP]Cl with cyclohexane and cyclohexanone as co-reactants. The results showed that the conversions of cyclohexane and cyclohexanone were significantly enhanced because of the cyclohexanone synergistic effect, and the higher selectivity to adipic acid was obtained with dioxygen as an oxidant. The studies indicated that the co-oxidation of cyclohexane and cyclohexanone was influenced by the initial molar ratio of cyclohexanone and cyclohexane, catalyst structure, catalyst concentrations, and reaction conditions. The preliminary mechanism of the co-oxidation reaction of cyclohexane and cyclohexanone using [MnIIIT(p-Cl)PP]Cl as the catalyst was proposed.

scholarly journals Biodiesel Production from a Novel Nonedible Feedstock, Soursop (Annona muricata L.) Seed Oil

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2562 ◽  
Author(s):  
Chia-Hung Su ◽  
Hoang Nguyen ◽  
Uyen Pham ◽  
My Nguyen ◽  
Horng-Yi Juan
Keyword(s):  
Reaction Time ◽  
Seed Oil ◽  
Biodiesel Production ◽  
Molar Ratio ◽  
Annona Muricata ◽  
Reaction Conditions ◽  
Biodiesel Feedstock ◽  
Acid Catalyzed ◽  
American Society ◽  
Optimal Reaction

This study investigated the optimal reaction conditions for biodiesel production from soursop (Annona muricata) seeds. A high oil yield of 29.6% (w/w) could be obtained from soursop seeds. Oil extracted from soursop seeds was then converted into biodiesel through two-step transesterification process. A highest biodiesel yield of 97.02% was achieved under optimal acid-catalyzed esterification conditions (temperature: 65 °C, 1% H2SO4, reaction time: 90 min, and a methanol:oil molar ratio: 10:1) and optimal alkali-catalyzed transesterification conditions (temperature: 65 °C, reaction time: 30 min, 0.6% NaOH, and a methanol:oil molar ratio: 8:1). The properties of soursop biodiesel were determined and most were found to meet the European standard EN 14214 and American Society for Testing and Materials standard D6751. This study suggests that soursop seed oil is a promising biodiesel feedstock and that soursop biodiesel is a viable alternative to petrodiesel.

Preparation of YBa2Cu3O7−x precursors from a fused eutectic of sodium and potassium hydroxides

1989 ◽  
Vol 4 (6) ◽  
pp. 1307-1311 ◽  
Author(s):  
Nicholas Coppa ◽  
Daniel H. Nichols ◽  
John W. Schwegler ◽  
J. E. Crow ◽  
G. H. Myer ◽  
...  
Keyword(s):  
Thermal Decomposition ◽  
Potassium Hydroxide ◽  
Product Formation ◽  
Mechanical Grinding ◽  
Reaction Conditions ◽  
Fine Powders ◽  
Yttrium Barium ◽  
Sodium And Potassium

A method for preparing YBa2Cu3O7−x from the simultaneous thermal decomposition of the nitrates of yttrium, barium, and copper in an anhydrous fused eutectic of sodium and potassium hydroxide is described. This method eliminates the need for any mechanical grinding or the introduction of carbon containing anions. Products formed are fine powders (∼1 μm) having mole ratios 1.00Y:2.00Ba:3.06Cu.X-ray diffraction analyses reveal that the initial products are Y(OH)3, BaO2, and CuO, which when air calcinated/oxygen annealed at 900–950 °C form the superconducting YBa2Cu3O7−x A mechanism is postulated for product formation as a function of reaction conditions.

scholarly journals Use of an Asparaginyl Endopeptidase for Chemo-enzymatic Peptide and Protein Labeling

2020 ◽  
Author(s):  
Simon Tang ◽  
Davide Cardella ◽  
Alexander J. Lander ◽  
Xuefei Li ◽  
Yu-Hsuan Tsai ◽  
...  
Keyword(s):  
Phenylboronic Acid ◽  
Product Formation ◽  
Protein Labeling ◽  
Recognition Sequence ◽  
Reaction Conditions ◽  
Site Specific ◽  
Asparaginyl Endopeptidase ◽  
Coupling System ◽  
Labeling System ◽  
Specific Peptide

Transpeptidases are ideal biocatalysts for site-specific peptide and protein labeling, whereas reactions that target N-terminus cysteine with commercially available reagents have become common practice. However, a versatile approach that allows bioconjugation at the terminus of choice (N or C), while avoiding the use of backbone-modified substrates (<i>e.g.</i> depsipeptide) or large excess of reagent, is highly desirable. Aiming to meet these benchmarks, we have combined the advantages of asparaginyl endopeptidase (AEP) catalysis with a N-terminal cysteine trapping reaction and created a chemo-enzymatic labeling system. In this approach, polypeptide with a Asn-Cys-Leu recognition sequence are ligated with a counterpart possessing an N-terminal Gly-Leu by AEP; the byproduct Cys-Leu is subsequently trapped by a stable and inexpensive scavenger, 2-formyl phenylboronic acid (FPBA), to yield an inert thiazolidine derivative, thereby driving the reaction forward to product formation. By carefully screening the reaction conditions for optimal compatibility and minimal hydrolysis, conversion to the ligated product in the model reaction resulted in excellent yields. The versatility of this AEP ligation/FPBA coupling system was further demonstrated by site-specific labeling the N- or C-termini of various proteins.

scholarly journals Morpholin-2-one Derivatives via Intramolecular Acid-Catalyzed Hydroamination

Synthesis ◽  
2019 ◽  
Vol 51 (07) ◽  
pp. 1643-1648 ◽  
Author(s):  
David Knight ◽  
Thomas Wirth ◽  
Abdul Hadi Aldmairi
Keyword(s):  
Amino Acids ◽  
Catalytic Amount ◽  
Practical Method ◽  
Trifluoromethanesulfonic Acid ◽  
Reaction Conditions ◽  
Available N ◽  
Metal Free ◽  
Acid Catalyzed

Substituted morpholin-2-one derivatives were readily obtained in two steps starting from commercially available N-protected amino acids. In a metal-free and practical method, a catalytic amount of trifluoromethanesulfonic acid was sufficient to generate morpholinones under mild reaction conditions in an intramolecular hydroamination reaction in good to excellent yields.

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