Friedel-Crafts acylation of aromatic compounds with carboxylic acids in the presence of P2O5/SiO2 under heterogeneous conditions

A convenient and efficient procedure for the Friedel-Crafts acylation of aromatic compounds with carboxylic acids in the presence of P₂O₅/SiO₂ is described. Both aromatic and aliphatic carboxylic acids reacted easily to afford the corresponding aromatic ketones. The use of non-toxic and inexpensive materials, simple and clean work-up, short reaction times and good yields of the products are the advantages of this method.     

A simple and efficient synthesis of 2-substituted benzothiazoles catalyzed by H_2O_2/HC1

A simple and efficient procedure for the synthesis of substituted benzothiazoles through condensation of 2-aminothiophenol with aromatic aldehydes in the presence of H₂O₂/HCl system in ethanol at room temperature is described. The target compounds have been characterized by ¹H NMR, ¹³C NMR, IR and MS. Short reaction time, easy and quick isolation of the products, and excellent yields are the main advantages of this procedure.     

H6P2W18O62·14H2O as an efficient catalyst for the green synthesis of α-aminophosphonates from α-amino acids

Abstract

A simple, efficient and eco-friendly protocol has been described for the synthesis of α-aminophosphonates via Kabachnik-Fields reaction, catalyzed by H₆P₂W₁₈O₆₂·14H₂O as a reusable catalyst. The reaction was realized by condensation of amino acids, various aromatic aldehydes and triethylphosphite under solvent-free conditions, the corresponding α-aminophosphonates were formed in good yields. All the new products were characterized by IR, ¹H, ¹³C and ³¹P-NMR analyses. This method offers advantages such as simplicity workup with the green aspects, good yields and short reaction times.     

Silver nitrate-catalyzed oxidation of aldehydes to carboxylic acids by H2O2

A variety of aromatic, aliphatic and conjugated aldehydes were converted to the corresponding carboxylic acid derivatives with 30% H₂O₂ as the oxidant in the presence of catalytic amounts of AgNO₃. The method described has wide range of applicabilities, does not involve cumbersome work-up, exhibits chemoselectivity and proceeds under mild reaction conditions, and the resulting products are obtained in good yields within reasonable time.     

NaHSO4·H2O as a Heterogeneous Acidic Reagent for Mild and Convenient Synthesis of 3,4-Dihydropyrimidin-2(1H)-ones and Their Sulfur Derivatives

One-pot cyclocondensation reaction of aromatic aldehydes, 1,3-dicarbonyl compounds and urea/thiourea in the presence of NaHSO₄·H₂O produced 4-aryl substituted 3,4-dihydropyrimidin-2(1H)-ones and their sulfur analogs in high to excellent yields. The reactions were carried out in refluxing n-hexane and were completed within 2.5–11 h.     

Ultrasound-Mediated Synthesis of 3,4-Dihydropyrimidin-2-(1H)-Ones (or Thiones) with NaHSO4·H2O

Abstract

A fast and efficient Biginelli synthesis of 3,4-dihydropyrimidin-2-(1H)-ones (or thiones) by the reaction of aromatic aldehydes, β-dicarbonyls, and urea/thiourea using NaHSO₄·H₂O/ultrasound system is presented. The reactions were carried out in refluxing n-hexane/CH₃CN (2.5:0.5 mL) to afford the products in excellent yields.     

Sonocatalyzed facile synthesis of 2-aryl benzoxazoles using MnO2 nanoparticles as oxidant agent under mild conditions

Nano MnO₂ was found to be an efficient oxidant agent for the synthesis of 2-substituted benzoxazoles through one-pot reaction of o-aminophenol and different aromatic aldehydes in acetonitrile under ultrasonic irradiation. This method was performed under mild conditions with high yields, inexpensive and readily available oxidant agent, facile and easy experimental procedure, simple purification of final products, and short reaction times. The prepared nano MnO₂ has been characterized by FTIR, XRD, and SEM techniques. The pure products were identified and characterized by physical and spectroscopic data such as; melting point, IR, ¹H NMR, and ¹³C NMR.     

Aldol Condensations Catalyzed by PEG400 and Anhydrous K2CO3 Without Solvent

Abstract

Aldol condensations of aromatic aldehydes with ketones under solvent‐free conditions to synthesize α,β‐unsaturated ketones in good to excellent yields using PEG400 and powdered anhydrous K₂CO₃ as catalysts at 90 °C and 120 °C are described.     

Multicomponent Domino Process for the Synthesis of Some Novel Benzo[a]chromenophenazine Fused Ring Systems Using H2SO4, Phosphotungstic Acid,and [NMP]H2PO4

Efficient, mild, and quantitative procedures for the synthesis of functionalized benzo[c]chromeno[2,3-a]phenazine derivatives by one-pot, four-component condensation of 2-hydroxynaphthalene-1,4-dione, 1,2-phenylenediamines, aromatic aldehydes, and cyclic 1,3-dicarbonyl compounds have been developed using catalytic amounts of H₂SO₄ and phosphotungstic acid in EtOH/H₂O (1:1) under reflux and also with [NMP]H₂PO₄, which acts as catalyst and medium at 80 °C. The reaction avoids tedious workup procedure due to the direct precipitation of products from the reaction medium. The present finding provides promising synthetic strategies for the synthesis of libraries with functional group diversity.     

Synthesis of 3,4-Dihydropyrimidin-2(1H)-ones Using Ce(SO4)2-SiO2 as a Heterogeneous and Recyclable Catalyst

A simple and efficient synthesis of 3,4-dihydropyrimidinones or thiones is described, using silica-supported ceric sulfate [Ce(SO₄)₂-SiO₂] as a heterogeneous catalyst from an aldehyde, 1,3-dicarbonyl compound, and urea or thiourea at 110 °C under solvent-free conditions. Compared with the classical Biginelli reaction, this new method consistently has better yields, short reaction time, easy separation, and tolerance toward various functional groups.     

Facile one-pot synthesis of 2-arylbenzothiazoles catalyzed by H3PO4/TiO2-ZrO2 (1/1) under solvent-free conditions

A highly efficient and simple protocol for the preparation of 2-arylbenzothiazoles through condensation of 2-aminothiophenol and different aldehydes in the presence of H₃PO₄/TiO₂-ZrO₂(1/1)-cetyl pyridinium bromide (CPB) is described. The reaction proceeded under mild and solvent-free conditions to afford 2-arylbenzothiazole derivatives. In this method, the title compounds were obtained in good to excellent yields and short reaction times. The structures of synthesized products were identified by infrared, ¹H NMR, ¹³C NMR, and mass spectroscopy.     

An effective aza-Michael addition of aromatic amines to electron-deficient alkenes in alkaline Al2O3

Aza-Michael addition of aromatic or aliphatic amines with various electron-deficient alkenes was performed using alkaline Al₂O₃ as solid media at room temperature afforded the corresponding Michael addition products in good to excellent yields. The alkaline Al₂O₃ can be easily recovered and reused.     

A rate enhancement of tert-butoxycarbonylation of aromatic amines with Boc2O in alcoholic solvents

A rate enhancement of tert-butoxycarbonylation of aromatic amines by Boc₂O in alcohols compared to aprotic solvents was demonstrated. Kinetic analysis by NMR suggested that the reaction in CD₃OD was faster than in CDCl₃ by a factor of 70. Reactions between Boc₂O and various aliphatic and aromatic amines in ethanol provided the N-Boc derivatives in good to excellent yields in short reaction times.     

Acetamide/SO2Cl2 as an efficient reagent for Friedel–Craft’s acylation of aromatic compounds under ultrasonic and microwave conditions

Acetamide/SO₂Cl₂ reagent has been developed for effective Friedel–Craft’s acylation of aromatic compounds. Acylation of aromatic compounds with acetamide/SO₂Cl₂ was much more effective and faster than analogous (acetamide/SOCl₂) and (acetamide/POCl₃) reagents even under conventional conditions. However, microwave and ultrasonic assisted reactions afforded high yields of products in very short reaction times (30–40 min under sonication and 3–4 min under microwave assisted conditions).     

Ferric sulfate [Fe2(SO4)3·xH2O]: an efficient heterogeneous catalyst for the synthesis of tetrahydroquinoline derivatives using Povarov reaction

Fe₂(SO₄)₃·xH₂O can be used as an efficient and reusable catalyst for the synthesis of pyrano- and furanotetrahydroquinolines via one-pot three-component Povarov reaction involving aromatic aldehydes, aromatic amines, and cyclic enol ethers. The catalyst is recyclable, economically viable, and environmentally benign. This protocol provides good yields and diastereoselectivity as well as applicability on a wide range of substrates.     

K2CO3促进苯并呋喃单元3-位与硫酚构建C-S键

本文在前期工作基础上进一步考察了2-位支链酮苯并呋喃单元在3位与硫酚构建C-S键的反应。研究发现,以K₂CO₃作碱,苯并呋喃单元2-位官能团为不同链长的脂肪酮时能高效地合成各种不同取代基的3-芳硫基苯并呋喃衍生物,所得产物经核磁共振、HRMS等方法进行了表征。该反应具有条件温和、底物适用范围广、操作简单、产率高、环境友好等优点,可为含有芳香烃硫基取代的天然产物及复杂药物分子的合成提供潜在的合成途径。     

Fe（HSO4）3： An efficient,heterogeneous and reusable catalyst for the synthesis of 14-aryl- or alkyl- 14H-dibenzo[a,j]xanthenes

Fe（HSO4）3 has been used as an efficient and recyclable catalyst for the one-pot synthesis of 14-aryl- or alkyl-14Hdibenzo[aj]xanthene derivatives by the reaction of 2-naphtol and aldehydes. Different types of aromatic and aliphatic aldehydes are used in the reaction and in all cases the products were obtained in good to excellent yields.     

Silica-supported perchloric acid and potassium bisulfate as reusable green catalysts for nitration of aromatics under solvent-free microwave conditions

Silica-supported perchloric acid and bisulfate (SiO₂/HClO₄ and SiO₂/KHSO₄) have been developed as reusable green catalysts for nitration of aromatic compounds using NaNO₂ in acetonitrile medium under conventional and solvent-free microwave conditions. The reaction times under microwave irradiation are significantly shorter than conventional method even though the yields obtained in microwave-assisted reactions are comparable with those obtained under reflux conditions.     

Ce(SO4)2·4H2O as a Recyclable Catalyst for an Efficient,Simple, and Clean Synthesis of 4H-Benzo[b]pyrans

An efficient method for the synthesis of 4H-benzo[b]pyrans has been developed by the use of Ce(SO₄)₂·4H₂O (2.5 mol%) as a catalyst. Heating the mixture of an appropriate aldehyde, malononitrile, and dimedone in the presence of the catalyst at 45°C in a mixture of water:ethanol (1:1) as solvent for about 9–55 min resulted excellent yields of the corresponding products. Short experimental time of the reaction, excellent yields, simple workup, not using cumbersome apparatus for purification of the products, and inexpensiveness and commercially availability of the catalyst are the advantages of this method.     

Simple and Efficient Procedure for the Friedel–Crafts Acylation of Aromatic Compounds with Carboxylic Acids in the Presence of P2O5/AL2O3 Under Heterogeneous Conditions

An efficient and chemoselective method for the Friedel–Crafts acylation of aromatic compounds using P₂O₅/Al₂O₃ and carboxylic acids. Both aromatic and aliphatic carboxylic acids reacted easily to afford the corresponding aromatic ketones in good yields.