Efficient Method for the Synthesis of 1,5‐Benzodiazepine Derivatives Catalyzed by Monoammonium Salt of 12‐Tungstophosphoric Acid

Monoammonium salt of 12‐tungstophosphoric acid [(NH₄)H₂PW₁₂O₄₀] was found to be a practical, inexpensive, reusable, and efficient heterogeneous catalyst for the preparation of 1,5‐benzodiazepine derivatives of o‐phenylenediamine and ketones. The heteropolyacid‐based catalyst has the advantages of simple workup procedure, water insolubility with good activity, and high‐yielding reaction for the synthesis of 1,5‐benzodiazepine derivatives.     

Simple and Efficient Method for the Synthesis of Benzimidazole Derivatives using Monoammonium Salt of 12‐Tungstophosphoric Acid

Benzimidazoles have been synthesized in very good yield from o‐phenylenediamine and aromatic aldehydes in the presence of monoammonium salt of 12‐tungstophosphoric acid [(NH₄)H₂PW₁₂O₄₀], an efficient heterogeneous catalyst. This catalyst has the advantages of simple workup procedure, water insolubility, and good activity with high yield for the synthesis of benzimidazole derivatives.     

Esterification and Selective Esterification in the Presence of TiCl4

A series of carboxylic acids was esterified to the corresponding esters with TiCl_4 as catalyst at room temperature,in high yields.This catalyst was highly effective for the selective esterification of primary alcohols with carboxylic acids,in the presence of secondary alcohols,and for the selective esterification of saturated acid with alcohol in the presence of conjugated acid or aromatic acid.On account of the high yield,high chemoselectivity,mild condition,and being free of other dehydrants,this is an efficient method.     

Esterification of Glycerol by Oleic Acid and Selective Hydrogenation of Oleic Acid Methylester Over Acid and Ru-Sn-B Supported Mesoporous AlMCM-41

Demand for large pore size molecular sieves has given rise to great interests in a new family of silica-based mesoporous materials designated as M41s, which expand typical molecular sieves into an extra-large pore range and generate the potential for the applications of these materials in catalysis and sorption for very bulky molecules1-6. MCM-41 possesses a hexagonal arrangement of uniform mesopore ranging from 15 to 100 ? and can be prepared with varied Si/Al ratios. The investigations of …     

Efficient CuCl-Catalyzed Selective and Direct Oxidation of β- and γ-Substituted Aliphatic Primary Alcohols to Carboxylic Acids

A new procedure for the selective and direct oxidation of aliphatic primary alcohols having substitution at β- and γ-positions to corresponding carboxylic acids was developed using a catalytic amount of ligand and additive-free CuCl with anhydrous ^t BuOOH in acetonitrile solvent under very mild reaction conditions. This procedure is very simple and mild and works efficiently without any additives at room temperature.     

RAFT Polymerization of Styrene in the Presence of 2‐Nonyl‐benzoimidazole‐1‐carbodithioic Acid Benzyl Ester

A novel dithiocarbamate, 2‐nonyl‐benzoimidazole‐1‐carbodithioic acid benzyl ester ( 1a ), was synthesized and successfully used in RAFT polymerization of styrene in bulk with thermal initiation. The effect of molar ratio of styrene to RAFT agent on the polymerization was investigated. The linear relationship between ln([M]₀/[M]) and polymerization time indicated that the polymerization was first‐order with respect to monomer concentration. The molecular weights increased linearly with monomer conversion and were close to corresponding theoretical values. The molecular weight distributions (M _w /M _n ) kept very narrow (M _w /M _n <1.1) at a wide range of conversions of 14.2% to 73.3%. The obtained polymer had a strong ultraviolet absorption at 329 nm, which indicated that the 1a moiety remained at the end of polymer chain.     

Polymer Supported Synthesis of 2,3,4,6-Tetra-O-Acetyl-β-D-Glucopyranosyl Esters of Aromatic Carboxylic Acids

Aromatic carboxylic acids bound to Amberlyst A-26 react with α-acetobromoglucose to form 2,3,4,6-tetra-O-acetyl-1-0-aroyl-β-D-glucopy ranose derivatives in good yield. Glucosylation occurs satisfactorily with carboxylic acids and nitrophenols (pKa 7–4), but not with phenols whose pKa values are higher (pka ～ 10). Selective glucosylation at the carboxylic group is easily achieved in the case of phenolic acids.     

Influence of Carboxylic Acids on the Synthesis of Chlorohydrin Esters from 1,3‐Butanediol

The influence of diverse carboxylic acid on the preparation of chlorohydrin esters using a one‐pot esterification–chlorination reaction, in which one of the reagents (chlorotrimethylsilane) acts as solvent, is described. Whereas the acid with low pKa provided higher amounts of the 2‐chloro regioisomer, the ones with higher pKa rendered the 1‐chloro regioisomer in 80% yield. These results are in accordance with the mechanism proposed in a previous article.     

A Multiwall Carbon Nanotube-chitosan Modified Electrode for Selective Detection of Dopamine in the Presence of Ascorbic Acid

A novel multiwall carbon nanotube-chitosan modified electrode has been prepared. The modified electrode resolves the overlapping voltammetric response of dopamine and ascorbic acid into two well-defined peak by 212 mV. The mechanism of discrimination of dopamine from ascorbic acid is discussed. Dopamine can be determined selectively with the carbon nanotube-chitosan modified electrode. The electrode shows good sensitivity, selectivity and stability.     

Esterification of Carboxylic Acids and Diacids by Trialkyl Borate under Solvent- and Catalyst-Free Conditions

Esterification or transesterification reactions are usually carried out in the presence of homogeneous or heterogeneous catalysts. However, recently a new method was reported for the esterification of carboxylic acids by tributyl borate under solvent- and catalyst-free conditions. In order to show the synthetic ability of trialkyl borate esters in the esterification reactions, here, the esterification of other carboxylic acids and diacids by tributyl-, triisoamyl-, and tribenzyl borate under the same conditions were reported. Some of the prepared ester and diester products have found wide applications as plasticizers and synthetic ester base lubricants. The esterification reactions have been cleanly carried out in the absence of any solvent under catalyst-free conditions. The maximum rate belongs to isoamyl trichloroacetate （VIb） which reached about 76% within about 6.5 h. On the basis of obtained findings, it seems that electron withdrawing groups on carboxylic acid facilitate the esterification reaction.     

Efficient Esterification of Ferrocenecarboxylic Acid in Ionic Liquids

An efficient esterification of ferrocenecarboxylic acid with substituted phenols has been achieved using DCC / DMAP protocol in ionic liquids. The corresponding esters are produced in high yields.     

Efficient and Rapid Method for the Oxidation of Electron‐Rich Aromatic Aldehydes to Carboxylic Acids Using Improved Basic Hydrogen Peroxide

An efficient and rapid method for oxidation of electron‐rich aromatic aldehydes to their corresponding carboxylic acids in excellent yields was developed. It is based on the oxidation of methoxy‐substituted benzaldehydes in methanol with an improved aqueous basic hydrogen peroxide system. Benzaldehydes with electron‐withdrawing substituents are oxidized to the corresponding carboxylic acid in excellent yields under mild reaction conditions.     

Micellar Mediated Halodecarboxylation of α,β‐Unsaturated Aliphatic and Aromatic Carboxylic Acids—A Novel Green Hunsdiecker–Borodin Reaction

A Novel Hunsdiecker‐Borodin reaction (HBR) has been carried out efficiently with α,β‐unsaturated aliphatic and aromatic carboxylic acids by using N‐halo succinimides such as N‐chloro succinimide (NCS), N‐bromo succinimide (NBS), and N‐iodo succinimide (NIS) under micellar media. The reaction with α,β‐unsaturated aromatic carboxylic acids afforded β‐halo styrenes in excellent yield while α,β‐unsaturated aliphatic carboxylic acids underwent decarboxylation and to give corresponding halo derivatives. The reactions are dramatically accelerated in micellar media. This procedure works efficiently in CTAB (cetyl trimethyl ammonium bromide), SDS (sodium dodecyl sulfate), and TX (Triton‐X‐100) media under stirred conditions at room temperature. At reflux temperatures the yield of reaction products were further enhanced from good to excellent.     

Effect of Temperature on the Solubility of Short-Chain Carboxylic Acids in Water

The aqueous solubilities of pentanoic and hexanoic acids were measured between 298.15 and 333.15 K at intervals of 5.00 K. Nonlinear dependences were found for the variation of solubility with temperature. The temperature dependences of the solubility of the acids in water are described by nonlinear van’t Hoff plots. Experimental data were fitted by the method of least-squares to a second-order polynomial equation, which was then used to determine the differential solution enthalpies at selected temperatures. The values for the apparent Gibbs energy and the apparent entropy of solution are calculated.     

Synthesis of α-Aminoarylacetic Acids in the Presence of Phase Transfer Catalysts

Inearlierpublications""aone-stepphasetransfercatalyzedreactionforpreparingaaminoarylaceticacidsfromarylaldehydesandchloroform,usingquaternarysaltsorf3CDasphasetransfercatalyst,wasdescribed;Itwasalsoreportedthatsomereactionsundersonicationconditionoftenoccurmorerapidlyandeasily'.Wenowfindthatthisreactioncanbeadvantageouslyrealizedbyphasetransfercatalysisundersonication.Optimumreactionconditionsweredeterminedwithbenzaldehyde.Inthepresenceoflithiumchloride,theyieldnoticeablydecreases(seeTablel)…     

Synthesis of Functionalized 1‐Azadienes by Reaction of 2,6‐Dimethylphenyl Isocyanide and Acetylenic Esters in the Presence of CH Acids

The adducts produced in the reaction between 2,6‐dimethylphenyl isocyanide and acetylenic esters were trapped by 3‐chloroacetylacetone, dialkyl 2‐chloromalonates, or dimethoxy methoxymalonate to produce highly functionalized 1‐azadienes in good yields.     

Mechanochemical Reaction of Aromatic Ketones and Aldehydes in the Presence of Zn-ZnCl2

The solvent-free reactions of aromatic ketones and aldehydes in the presence of Zn-ZnCl2 were performed with the aid of high-speed vibration mill, Retsch MM200 mixer mill and Retsch RM100 mortar grinder to give pinacol coupling and reduction products in varying yields.     

Oxidation of Aldehydes and Ketones into Carboxylic Acids and Esters Using 4‐Amino‐2‐Chloroperbenzoic Acid Supported on Silica Gel

Abstract

4‐Amino‐2‐chloroperbenzoic acid supported on silica gel was found to be a versatile and efficient oxidant for the oxidation of aldehydes and ketones to the corresponding carboxylic acids and esters.     

Organic Reactions in Water: Synthesis of Phenacyl Esters from Phenacyl Bromide and Potassium Salts of Aromatic Acids in the Presence of β‐Cyclodextrin

Abstract

A convenient and facile synthesis of phenacyl esters is reported by the reaction of phenacyl bromide with potassium salts of aromatic acids in the presence of β‐cyclodextrin in water under neutral conditions.     

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.