Sulfamic Acid as a Cost-effective Catalyst for Acetolysis of Cyclic Ethers

Sulfamic acid has been used as an efficient catalyst and green alternative for conventional acidic materials to promote the acetolysis reaction of THF to produce 1,4-diacetoxybutane. This method is also applicable in the acetolysis of other cyclic ethers, such as methyl substituted THF and tetrahydropyran and 1,4-dioxane which is less reactivity.     

Facile and Highly Selective Deprotection of tert‐Butyldimethyl Silyl Ethers using Sulfated SnO2 as a Solid Catalyst

Highly selective deprotection of tert‐butyldimethylsilyl ethers at room temperature has been described using sulfated SnO₂ as an efficient solid catalyst.     

Wet Carbon‐Based Solid Acid/Potassium Bromate as an Efficient Heterogeneous Reagent for Oxidation of Alcohols under Mild Conditions

Wet carbon‐based solid acid and potassium bromate were used as new reagent for oxidation of alcohols to their corresponding aldehyde or ketone derivatives in dichloromethane with good yields.     

Silica‐Supported bis (Trimethylsilyl) Chromate: Oxidation of Thiols to Their Corresponding Disulfides

An efficient and convenient method for the oxidation of thiols mediated by silica‐supported bis (trimethylsilyl) chromate (BTSC) in acetonitrile is reported.     

Efficient Synthesis of β‐Acetylamino Ketones using Silica‐Supported Sodium Hydrogen Sulfate as a Heterogeneous Catalyst

Silica‐supported sodium hydrogen sulfate (NaHSO₄ · SiO₂) efficiently catalyzes the four‐component reaction of aryl aldehydes, enolisable ketones, acetyl chloride, and acetonitrile to form the corresponding β‐acetylamino ketones at room temperature. The catalyst is inexpensive and ecofriendly and works under heterogeneous conditions.The present methodology offers several advantages such as excellent yields, simple procedure, short reaction times (1–3 h), and mild conditions.     

Synthesis of 1‐Indanones via Intramolecular Cyclodehydration of 3‐Arylpropionic Acids Catalyzed by Heteropoly Acid as Heterogeneous Catalyst

Intramolecular cyclodehydration of 3‐arylpropionic acids catalyzed by heteropoly acids was investigated for the first time. Several 3‐arylpropionic acids were refluxed and dehydrated in chlorobenzene in the presence of 0.2 equivalent of heteropoly acids, and 1‐indanones were obtained in good yield. At the same time, intermolecular Friedel–Crafts acylation were observed in this experiment.     

Sulfamic Acid as an Effective Catalyst in Solvent‐Free Synthesis of β‐Enaminoketone Derivatives and X‐ray Crystallography of Their Representatives

Two types of β‐enaminoketone derivatives of 3‐(2‐oxo‐2‐arylethylidene)‐3,4‐dihydro‐1H‐quinoxalin‐2‐ones and 3‐(2‐oxo‐2‐arylethylidene)‐3,4‐dihydro‐benzo[1,4]oxazin‐2‐ ones were effectively and conveniently prepared in good to excellent yields under solvent‐free conditions via the catalysis of sulfamic acid in the corresponding condensations of o‐phenylenediamine and o‐aminophenol with ethyl 2,4‐dioxo‐4‐arylbutyrate respectively. The compounds were confirmed by IR, ¹H NMR, and ¹³C NMR, and a representative was further determined by X‐ray crystallography.     

Synthesis of a Novel Carbon Based Acid Catalyst and Its Catalytic Activity for the Acetalization and Ketalization

A novel carbon based strong solid acid catalyst has been synthesized successfully. The catalytic activity for acetalization and ketalization was investigated. The results showed that the novel catalyst was very efficient with the average yield over 92%. The novel heterogeneous catalyst also has the advantages of high activity, wide applicability even to the preparation of 7 membered ring acetals and ketals, strikingly simple workup procedure, non-pollution and reusability, which will contribute to the green process greatly.     

On Water: An Efficient Knoevenagel Condensation using 12‐Tungstophosphoric Acid as a Reusable Green Catalyst

12‐Tungstphosphoric acid is found to be an efficient, environmentally attractive, and reusable catalyst for Knoevenagel condensation of malononitrile and ethylcyanoacetate with various aldehydes.     

Sulfonic Acid–Functionalized Silica (SiO2-Pr-SO3H) as a Solid and a Heterogeneous Catalyst in Green Organic Synthesis: Recent Advances

The application of sulfonic acid–functionalized silica (SBA-Pr-SO₃H) as a catalyst in organic synthesis has become an efficient and green strategy for the selective construction of organic motifs. Therefore, the great efforts have been made by scientists to replace the conventional acid catalysts by sulfonic acid–functionalized silica used as solid, heterogeneous catalyst in various organic transformations. The sustainable advantage of sulfonic acid–functionalized silica is that it can be recovered and reused several times without loss of its efficiency. In this tutorial review, we attempt to give an overview about the use of sulfonic acid–functionalized silica as a catalyst in the synthesis of various organic compounds having industrial as well as pharmaceutical applications.     

Efficient Conversion of Tetrahydropyranyl (THP) Ethers to Their Corresponding Thiocyanates With in-situ–Generated Ph3P(SCN)2

Immediate and efficient one-pot conversion of tetrahydropyranyl (THP) ethers to their corresponding thiocyanates by in-situ–generated Ph₃P(SCN)₂ is described. Primary and secondary alkyls and also benzylic THP ethers are converted to their corresponding thiocyanates in excellent yields at room temperature by this method.     

Development of a Solid‐Phase Extraction‐Enzyme‐Linked Immunosorbent Assay Method with a New Sorbent of Multiwall Carbon Nanotube for the Determination of Estrone in Water

Abstract

A sensitive solid‐phase extraction‐enzyme‐linked immunosorbent assay (SPE‐ELISA) method was developed to analyze the estrone in environmental water. A new SPE sorbent of the multiwall carbon nanotube was tested and proved to have similar adsorbability for estrone comparing to the commercial C₁₈ SPE. A specific polyclonal antibody for estrone (A‐E1) and a broad‐spectrum antibody for estrone, estradiol and estriol (A‐E2) were produced. For A‐E1, the limit detection of estrone was 0.04 µg/l and for A‐E2 were 0.07, 0.04 and 0.2 µg/l of estrone, estradiol and estriol, respectively. Different river water samples were analyzed by ELISA and HPLC method.     

Microwave‐Induced Conversion of Acid Hydrazides to N,N′‐Diacylhydrazines in Solvent‐Free Conditions

A new and efficient method of converting acid hydrazides 1 to the corresponding N,N′‐diacylhydrazines 2 under microwave irradiation and in solvent‐free conditions has been described.     

Unprecedented Transformation of Thioglycosides to Their Corresponding 1‐O‐Acetates in the Presence of HClO4‐SiO2 §

An unprecedented conversion of thioalkyl/aryl glycoside to the corresponding 1‐O‐acetates has been described using acetic anhydride and HClO₄‐SiO₂ at rt. Although this transformation does not play an important role in the oligosaccharide synthesis in comparison to its reverse transformation, this gives useful information in selecting the reaction condition for the synthesis of oligosaccharides. The yields were excellent in all cases.     

Phosphotungstic Acid Nanoclusters Grafted onto High Surface Area Hydrous Zirconia as Efficient Heterogeneous Catalyst for Synthesis of Octahydroquinazolinones and β-Acetamido Ketones

Phostungstic acid (PWA) nanoclusters grafted onto high surface area polycrystalline hydrous zirconia powder (PWA/ZrO₂) was prepared by wet impregnation method. The zirconia particles were synthesized using a modified sol–gel route. The obtained material was characterized by X-ray diffraction (XRD), UV–Vis–diffuse reflectance spectroscopy (UV–Vis–NIR–DRS), infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and sorptometric techniques. XRD study revealed the presence of tetragonal phase of zirconia in the synthesized sample. TEM study indicates presence of small PWA clusters with size in the range of 5–15 nm well dispersed on the surface of the ZrO₂ particles. The characteristic UV and IR absorption feature of the PWA was retained in the PWA/ZrO₂ material. The PWA/ZrO₂ material was used as an efficient catalyst for the preparation of octahydroquinazolinones and β-acetamido ketones. The octahydroquinazolinones were synthesized by the multicomponent condensation of dimedones, urea and aryl aldehydes in ethanol. Similarly, β-acetamido ketones were synthesized with high yield and purity by four component condensation of aryl aldehydes, enolizable ketones, and acetyl chlorides in acetonitrile. The protocols developed in this investigation using the PWA/ZrO₂ catalyst is advantageous in terms of simple experimentation, high yield and purity of the products and recovery and reutilization of the heterogeneous catalyst.     

Sulfamic Acid as a Cost‐Effective and Recyclable Catalyst for Protection of Carbonyls to Acetals and Ketals Under Mild Conditions

Abstract

An efficient H₂NSO₃H‐catalyzed protection of various carbonyl compounds at room temperature was investigated. The features of mild conditions, cost‐efficient catalyst, simple workup, and the recyclability of the catalyst were represented in this process.     

Mild and Efficient Michael Addition of Activated Olefins to Indoles using TBAB as a Catalyst: Synthesis of 3‐Substituted Indoles

A mild and efficient method for the synthesis of 3‐substituted indoles by treatment of activated olefins with indoles using TBAB as a catalyst afforded the corresponding products in excellent yields. The method is general for the preparation of a wide variety of 3‐substituted indoles.     

Dibromomethane as One‐Carbon Source in Organic Synthesis: Formal Total Synthesis of (±)‐Nephrosteranic Acid

A diastereoselective formal total synthesis of (±)‐nephrosteranic acid (10) is described. The key step is to introduce the α‐methylene group by the ozonolysis of monosubstituted alkenes followed by reaction with a preheated mixture of CH₂Br₂–Et₂NH. The α‐methyl group of compound 10 was formed from the reduction of the corresponding α‐methylene precursor.     

Development of a Novel Solid‐State pH Sensor Electrode Based on Titanium Oxide Thin Film as an Indicator Electrode in Potentiometric Acid‐Base Titrations in Fused NaNO3 at 350°C

A solid‐state pH sensor was fabricated using a transparent conductive titanium oxide film on a glass substrate. The coating of the glass substrate was achieved by a novel simple chemical vapor deposition (CVD) procedure. The sensor slope was found to increase as the temperature of the solution was increased. The performance of the sensor was investigated in the pH range from 2.2 to 11.19. The E‐pH curve is linear with slope of 0.054 V at 298.15 K. This value is closed to the theoretical value 2.303RT/F (0.059 V at 298.15). The standard potential of this electrode, E°, is computed as 177.58 mV with respect to the SCE as reference electrode. Results obtained by the suggested sensor compares very well with conventional pH electrodes where the square of the correlation coefficient was 0.998. This electrode can be used as an indicator electrode in potentiometric acid‐base titration. This electrode behaves reversibly and responds to the oxide ion concentration in molten NaNO₃. K₂Cr₂O₇ was potentiometrically titrated with Na₂O₂ and K₂CO₃ as titrants in molten NaNO₃ at 350°C, using the above mentioned indicator electrodes. An acidity/basicity scale of the oxyanions was established in molten NaNO₃ at 350°C.