Acid-catalyzed Synthesis Research Articles

Ultrasound-assisted synthesis of novel undecylenic estolides: Modeling and Tribological characterization

Abstract To overcome the issues related to low-temperature characteristics and thermal degradation of fatty acid based lubricant base stocks, chemical modification is essential. To mitigate these shortcomings, considering unsaturated undecylenic acid, the formation of estolides is one of the best transformations considering application in lubricants. Ultrasonic-assisted sulfuric acid-catalyzed synthesis of estolides of undecylenic was modeled using response surface methodology (RSM) and subsequently validated using artificial neural network (ANN) for known and unknown input variables. At optimal reaction conditions of reaction temperature of 56°C, catalyst loading of 0.63 mole-equivalent, and reaction time of 1.61 hours, estolides with estolide number (EN) of 2.58, extraordinary low pour point (PP) of −52°C and better resistance to thermal degradation was obtained. The thermal degradation was evaluated using thermogravimetric analysis (TGA) to find improved resistance toward degradation due to the formation of estolides. Further, tribological properties like wear characteristics, load carrying capacity, and oxidative stability were studied for 5% blends in SN 70 base oil. The anti-wear ability of the estolides was found to be superior to undecylenic acid, with a lower coefficient of friction, scar diameter, depth, and volume. The blend containing estolide was found to have load carrying capacity as high as 800 kgf. Moreover, owing to the double bond migration during the reaction, the oxidative stability of estolides was found to be inferior to the terminally unsaturated undecylenic acid.

Glutamic acid-catalyzed synthesis of dihydroquinazolinone: anticancer activity, electrochemical behavior, molecular docking, dynamics, simulations and drug-likeness studies

Glutamic acid-catalyzed synthesis of dihydroquinazolinone: anticancer activity, electrochemical behavior, molecular docking, dynamics, simulations and drug-likeness studies

Brønsted acid-catalyzed synthesis of spirocyclobutanes via heteroannulation of vinyloxyphenylbicyclobutanes with water.

We report a perchloric acid-catalyzed heteroannulation for the synthesis of spirocyclobutanes using vinyloxyphenylbicyclobutanes with water. This metal-free reaction yields high product outputs and is consistent with the formation of a cyclobutene intermediate originating from an isomerization of a bicyclobutane.

Brønsted Acid-Catalyzed Synthesis of 4-Functionalized Tetrahydrocarbazol-1-ones from 1,4-Dicarbonylindole Derivatives.

A p-toluenesulfonic acid-catalyzed cascade reaction is reported for the synthesis of 4-functionalized tetrahydrocarbazolones via the reaction of 4-(indol-2-yl)-4-oxobutanal derivatives with a variety of nucleophiles in acetonitrile or hexafluoroisopropanol. After the initial intramolecular Friedel-Crafts hydroxyalkylation, the 3-indolylmethanol intermediate is subsequently activated and reacted with the external nucleophile. The reaction conditions are crucial to avoid alternative reaction pathways, allowing direct substitution reaction with thiols, (hetero)arenes, alkenes, or sulfinates. The procedure features high overall yields to access a diverse family of compounds bearing the tetrahydrocarbazole core.

The effect of the active site and substrate structure in preparation of substituted tetrahydropyrans via intramolecular cyclization

Substituted tetrahydropyrans (THPs) are important biologically active compounds and synthetic intermediates. Their prevalence and diverse applications make them desirable targets in synthetic organic chemistry. Current synthetic routes for THP synthesis involve homogeneous catalysts and usually multiple steps and the use of expensive heavy metal catalysts, which pose environmental concerns. Therefore, there is a need for alternative approaches that can enhance efficiency, eco-friendliness, and cost-effectiveness This study focuses on the acid-catalyzed synthesis of THPs through the intramolecular cyclization of substituted (E)− 5-phenylpent-4-en-1-ols over zeolites as heterogeneous catalysts. The study particularly focused on investigating the influence of functional groups, as well as substrate size, on the reaction outcome. The results demonstrated that electron-donating groups enhance the conversion of the reactants and increase selectivity towards THPs, while electron-withdrawing groups have the opposite effect. Furthermore, the cyclization reaction also occurred on substrates containing different aromatic cycles. However, the conversion of a bulky substrate containing naphthyl group decreased due to mass transfer limitations. The catalytic performance of different types of zeolites with diverse acid sites was also examined. Brønsted acidic zeolites such as Al-BEA and Ga-BEA exhibited promising catalytic performance and 94 % and 83 % selectivity towards THPs, respectively. In contrast, Lewis acidic zeolites such as Sn-BEA, Ti-BEA, and Zr-BEA showed conversions below 6.5 % and poor selectivity, showing that Brønsted acidic zeolites are more suitable for the cyclization reaction than Lewis acidic zeolites.

Phosphoric acid-catalyzed synthesis of fused pyridocoumarins and their acidochromic applications

Pyridocoumarins are well known to exhibit various potent applications in optoelectronics, fluorescent probes, and sensors due to their unique photophysical properties. A concise and effective approach has been demonstrated to synthesize pyridocoumarins via a relatively inexpensive phosphoric acid-catalyzed Povarov reaction and their photophysical properties has also been investigated. The structures of all the synthesized compounds were well characterized by using 1H NMR, 13C NMR, IR, HRMS, and single crystal X-ray structure analysis. Detailed spectroscopic studies revealed that all the synthesized pyridocoumarins displayed acidochromic properties in solutions, which could be utilized as acid-base vapor sensors, and anti-counterfeiting agents. The detection limit was also calculated for all the synthesized acid sensors, which were found to be in the range of 41–103.8 ppm (parts per million). DFT and TDDFT studies were also performed to understand the protonation sites and the electronic transitions involved in these compounds. HOMO–LUMO energy gap of the synthesized pyridocoumarins ranges from 3.50 to 3.90 eV.

Reaction mechanism and process safety assessment of acid-catalyzed synthesis of tert-butyl peracetate

Esterification during the synthesis of tert-butyl peracetate (TBPA) is highly exothermic. Since peroxides (tert-butyl hydroperoxide TBHP and TBPA) are intrinsically thermosensitive, this synthesis process is potentially dangerous. In this work, the exothermic process and mechanism of TBPA synthesis using acetic anhydride (Ac2O) and TBHP under the catalysis of sulphuric acid (H2SO4) were clarified by calorimetry, infrared spectroscopy, and high-performance liquid chromatography. To substantially alleviate the thermal risk of the reaction, and to feasibly select appropriate synthesis conditions for ensuring the process safety of the synthesized products, several sets of isothermal and isoperibol experiments were performed using calorimetry. The intermediates formed and concentration changes during the reaction were monitored using in-situ Fourier-transform infrared spectroscopy. Differential scanning calorimetry and adiabatic calorimetry were used to assess the thermal hazard of the materials during the synthesis process. The reaction mechanism was verified using density functional theory calculations. The results revealed that a controlled increase in exothermicity could be achieved by adding aqueous TBHP to Ac2O in semi-batch experiments in isothermal mode, and accordingly, the highest yield was 95.71%. Experiments combined with theoretical calculations revealed that the primary exothermic event was the TBPA formation reaction, and the removal of a large amount of water from TBHP prior to this is favourable for the reaction. The criticality classes of this reaction were of Grade 2.

Synthesis and Characterization of 3-Methyl-1-(4-(trifluoromethyl)phenyl)indeno [1,2-c]pyrazol-4(1H)-one

Pyrazoles have potential applications in the agrochemical and medicinal chemistry industries as pesticides, anti-inflammatory medications, and antitumor drugs. Fluorinated fused-ring pyrazoles may also possess medicinally useful properties. Herein, we report the acid-catalyzed synthesis of a new tricyclic, trifluoromethylated indenopyrazole, 3-methyl-1-(4-(trifluoromethyl)phenyl)indeno[1,2-c]pyrazol-4(1H)-one, from 2-acetyl-1,3-indanedione and 4-trifluoromethylphenylhydrazine. This isomeric pyrazole was obtained in yields ranging from 4–24%. NMR spectroscopic characterization and elemental analysis support the structural assignment, identity, and purity of the product.

Brønsted Acid-Catalyzed Synthesis of 1,2,5-Trisubstituted Imidazoles via a Multicomponent Reaction of Vinyl Azides with Aromatic Aldehydes and Aromatic Amines.

A facile and efficient approach to the synthesis of 1,2,5-trisubstituted imidazoles is developed via a multicomponent reaction under metal-free catalysis. Under Brønsted acid catalysis, the desired products can be obtained from readily available vinyl azides, aromatic aldehydes, and aromatic amines without generating any toxic waste. The convenient operations and high functional group compatibility indicate that this approach offers an attractive alternative method for the synthesis of imidazole derivatives.

Acid-catalyzed synthesis of pyrazolo[4,3-c]quinolines from (1H-pyrazol-5-yl)anilines and ethers via the cleavage of C–O bond

Acid-promoted the cyclization reaction for the synthesis of pyrazolo[4,3-c]quinolines from (1H-pyrazol-5-yl)anilines and ethers via the cleavage of C–O bond has been developed. This method exhibits the advantages of good functional group tolerance, simple reaction conditions and without addition of metal catalyst, providing novel products in moderate to good yields, which has potential applications in the organic, pharmaceutical chemistry.

Lewis Acid-Catalyzed Synthesis of Alkoxymethylhalides for Multipurpose Mixed Acetals; Scope and Limitations

Abstract: The work describes a detailed account of the Lewis acid-catalyzed preparation of structurally variant alkoxymethyl halides. A series of Lewis acids with different halogenating agents are evaluated for the cleavage of bis-alkoxymethanes, where several readily available Lewis acids were found to exhibit high catalytic potential. SOCl2 with MgCl2 was found to be one of the best combinations for the facile and efficient preparation of structurally diverse alkoxymethyl halides under solvent-free conditions. The efficacy of the methodology was established to obtain a wide range of mixed acetals through alkoxymethylation of phosphorus, sulfur, nitrogen, and oxygen containing nucleophiles. The present procedure has significant advantages including simplicity, generality, rapidity, and availability of reagents.

Lewis Acid-Catalyzed Synthesis of Polysubstituted Furans from Conjugated Ene-yne-ketones and 1,3,5-Triazinanes.

An efficient and metal-free approach to the construction of diverse functionalized furan derivatives has been developed from ene-yne-ketones and 1,3,5-triazinanes. As an atom-economical and environment-friendly protocol, the new conditions are suitable for selective C-N and C-O bond formation of a wide range of polysubstituted furans in one pot.

Single-step acid-catalyzed synthesis of luminescent colloidal organosilica nanobeads

We present a single-step, room-temperature synthesis of fluorescent organosilica nanobeads (FOS NBs). The FOS NBs were synthesized under aqueous conditions using (3-aminopropyl)triethoxysilane (APTES) as the silicon source in the presence of l-ascorbic acid (L-AA). In the APTES/L-AA/water ternary phase, the hydrolysis and condensation reaction of APTES occurred under acidic conditions to form spherical FOS NBs with an average diameter of 426.8 nm. FOS NBs exhibit excellent colloidal stability in aqueous media. The formation of FOS NBs was complete within a 10 min reaction time, which indicates potential for large-scale mass-production synthesis of luminescent colloidal NBs. The FOS NBs exhibited blue photoluminescence (PL) under UV excitation in the absence of an additional high temperature calcination process or with the incorporation of any fluorophores. This phenomenon is attributed to the presence of carbon-containing defects, which act as luminescent centers formed by the reaction between amino groups in the APTES and l-ascorbic acid reductant. Finally, the results of a cytotoxicity test and cellular uptake experiments revealed that the FOS NBs showed potential as optical contrast agents for bioimaging.Graphical

Bronsted Acid-Catalyzed Synthesis of Spirolactams by Dearomatization of (Het)arenes

Key words ynamides - phosphoric acid catalysis - hetarenes - Claisen rearrangement - asymmetric catalysis - spirolactams

Silica-Supported Molybdic Acid-Catalyzed Synthesis of New and Known Chromeno-Pyrano[2,3-b]Quinolines through a Green Route

A capable manner for the preparation of chromeno-pyrano[2,3-b]quinoline compounds is outlined. Pyrano[3,2-c]chromene-3-carbonitriles are synthesized via the one pot three-component reaction of aryl aldehydes, malononitrile and 4-hydroxycoumarin in the presence of silica sodium carbonate (SSC) as a heterogeneous basic catalyst. Next, the prepared pyrano[3,2-c]chromene-3-carbonitrile is reacted with cyclohexanone by using silica-supported molybdic acid (SSMA) as a worthy and recyclable catalyst for producing recognized and unrecognized chromeno-pyrano[2,3-b]quinoline derivatives under solvent-free conditions in good to excellent yields.

Acid-Catalyzed Synthesis of pyrazolo[4,3-C]quinolines From (1H-Pyrazol-5-Yl)anilines and Ethers via the Cleavage of C−O Bond

Acid-Catalyzed Synthesis of pyrazolo[4,3-C]quinolines From (1H-Pyrazol-5-Yl)anilines and Ethers via the Cleavage of C−O Bond

Recent advances in the asymmetric phosphoric acid-catalyzed synthesis of axially chiral compounds.

In recent years, the synthesis of axially chiral compounds has received considerable attention due to their extensive application as biologically active compounds in medicinal chemistry and as chiral ligands in asymmetric catalysis. Chiral phosphoric acids are recognized as efficient organocatalysts for a variety of enantioselective transformations. In this review, we summarize the recent development of chiral phosphoric acid-catalyzed synthesis of a wide range of axially chiral biaryls, heterobiaryls, vinylarenes, N-arylamines, spiranes, and allenes with high efficiency and excellent stereoselectivity.

Triflic Acid-Catalyzed Synthesis of Indole-Substituted Indane Derivatives via In Situ Formed Acetal-Facilitated Nucleophilic Addition and 4π-Electron-5-Carbon Electrocyclization Sequence.

An efficient protocol for the synthesis of indole-substituted indanes from o-alkenylbenzaldehydes under acetalization conditions has been presented. The cyclization occurs via a nucleophilic addition of indole on the oxacarbenium ion generated from acetal formed under the reaction condition followed by a conrotatory 4π-electrocyclization reaction, which takes care of the exclusive diastereoselectivity observed during the cyclization step. Olefin geometry of o-alkenylbenzaldehyde and the amount of indole play a decisive role in the success of this cyclization process.

Chiral Phosphoric Acid-Catalyzed Synthesis of α-Amino Esters

Key words phosphoric acids - sulfoxonium ylides - amines - amino esters - asymmetric catalysis

Strong acid-catalyzed electrophilic ring expansion of oxetanes and sulfoxonium ylides

• Protic acid-catalyzed synthesis of functionalized trans -disubstituted tetrahydrofurans. • Electrophilic ring expansion reaction of sulfoxonium ylides to oxetanes was developed. • A transition metal-free ring expansion reaction of oxetanes to tetrahydrofurans. • Ring expansion of oxetanes to tetrahydrofurans with safe and stable ylides. • Stereospecific synthesis of functionalized trans -2,3-disubstituted tetrahydrofurans. A strong protic acid-catalyzed electrophilic ring expansion of oxetanes into trans -2,3-disubstituted tetrahydrofuran derivatives using sulfoxonium ylides has been developed. This reaction produces functionalized trans -2,3-disubstituted tetrahydrofuran derivatives stereospecifically by using safe and stable sulfoxonium ylides without metal catalysts and the protection of inert gas.