A one-pot synthesis of nitrogen-containing heteroaryl α-keto amides from heteroaryl halides

The S_NAr-type reaction of the piperidine amide of cyanoacetic acid with a series of heteroaryl halides followed by in situ oxidation of the resultant anion with peracetic acid provided a convenient, one-pot protocol for preparative access to heteroaryl α-keto amides. In this procedure, the amide of cyanoacetic acid functions as an Umpolung-type synthon of the α-keto amide moiety.     

Indirect electrosynthesis of peracetic acid using hydrogen peroxide generated in situ in a gas diffusion electrode

Indirect electrochemical oxidation of acetic to peracetic acid in aqueous solutions using hydrogen peroxide generated in situ from O₂ in a gas diffusion electrode was studied. The use of sulfuric acid and ammonium molybdate as catalysts accelerated the formation of peracetic acid during the electrolysis, and the use of both catalysts allowed us to prepare 0.02 M solutions. The limiting stage of the electrosynthesis of peracetic acid was the chemical interaction of the substrate with the generated H₂O₂. The desired product mainly formed during the storage of the reaction mixture after the electrosynthesis. In electrolytes with more than 3.5 M acetic acid, the electrochemical activity of the gas-diffusion cathode decreased.     

2-Ethoxy-3-pyridylboronic acid: a versatile reagent for the synthesis of highly-functionalised 3-aryl/heteroaryl-pyridines via Suzuki cross-coupling reactions

This paper describes the commercially-viable synthesis and isolation of 2-ethoxy-3-pyridylboronic acid on a ca. 70 g scale via a directed ortho-metalation reaction on readily-available 2-ethoxypyridine. A range of efficient cross-coupling reactions of 2-ethoxy-3-pyridylboronic acid with selected aryl/heteroaryl halides under palladium-catalysed Suzuki-Miyaura conditions yield novel 2-ethoxy-3-aryl/heteroaryl-pyridines in high yield (heteroaryl=pyridyl, pyrimidyl, pyrazyl). The X-ray crystal structure of 2-ethoxy-3-pyridylboronic acid reveals that the boronic acid group takes part in an intramolecular O-H?O bond with the adjacent ethoxy substituent, and an intermolecular O-H?N bond.     

Efficient synthesis of 4‐heteroaryl‐substituted triphenylamine derivatives via a ligand‐free Suzuki reaction

This paper reports an efficient synthesis of 4‐heteroaryl‐substituted triphenylamine derivatives via the palladium‐catalyzed Suzuki reaction of heteroaryl halides with 4‐(diphenylamino)phenylboronic acid in ethylene glycol under ligand‐free and aerobic conditions. These derivatives are important structural motifs for use in dye‐sensitized solar cells and organic electroluminescence materials. Copyright © 2011 John Wiley & Sons, Ltd.     

Novel Synthesis of 6‐Substituted 2‐Picolines from Aryl/heteroaryl β‐Enaminones and Meldrum's Acid Using CeCl3.7H2O/NaI

One‐pot condensation of aryl/heteroaryl β‐enaminones, Meldrum's acid, and ammonium acetate in the presence of CeCl₃.7H₂O/NaI via tandem Michael addition–cyclodehydration–elimination sequence led to the formation of novel regioselective 6‐substituted 2‐picolines.     

Oxidative addition of heteroaromatic halides to Negishi reagent and subsequent cross-coupling reactions

Heteroarylzirconocene halides were prepared via the oxidative addition of heteroaryl halides to the Negishi reagent ‘Cp₂ZrBu₂’. The palladium-catalyzed cross-coupling of the in situ generated organozirconium reagents with functionalized aryl and heteroaryl halides proceeded smoothly in the presence of CuCl to produce the cross-coupling products in high yields.     

过氧乙酸催化氧化亚硫酸钙的反应动力学

利用间歇式反应装置, 研究了过氧乙酸催化氧化亚硫酸钠的本征反应动力学, 得到各反应物的分级数及表观活化能. 在此基础上, 利用鼓泡式反应装置, 通过改变pH、亚硫酸钙浓度、过氧乙酸浓度、空气流量及温度, 研究了过氧乙酸催化氧化亚硫酸钙的宏观反应动力学.     

Catalyst-Free Intermolecular Sulfonyl/Fluoromethyl Heteroarylation of Vinyl Ethers via Visible-Light-Induced Charge Transfer

We report a visible-light-induced three-component sulfonyl-heteroarylation of vinyl ethers with sulfinates and five-membered heteroaryl chlorides. This protocol proceeds via electron-donor-acceptor (EDA) complexes between sulfinates and heteroaryl chlorides, giving β-sulfonyl alkyl five-membered heteroarenes with high efficiency and excellent regioselectivity under mild and catalyst-free conditions. Utilization of CF₃SO₂Na or CF₂HSO₂Na as coupling partners further achieves three-component fluoromethyl-arylation of vinyl ethers, furnishing a series of valuable CF₃/CF₂H-incorporated alkyl heterocycles under mild conditions.     

Synthesis of substituted aryl amidines from aminoacetonitriles

Aryl aminoacetonitriles are oxidized by NiO₂-H₂O or MnO₂ in the presence of a wide range of NH₂-containing compounds to afford aryl amidines, presumably via iminium intermediates. A ‘one-pot’ procedure for the preparation of heteroaryl amidines from N-containing heteroaryl halides through a process comprising sequential S_NAr substitution and oxidation has also been developed.     

Solvent-free Brønsted acid catalysed alkylation of arenes and heteroarenes with benzylic alcohols

A simple and efficient alkylation of aromatic and heteroaromatic compounds via the direct S_N1-type nucleophilic substitution of benzylic alcohols in the presence of catalytic amounts of the strong Brønsted acid o-benzenedisulfonimide under neat conditions is herein reported. A library of di- and triaryl (and heteroaryl) methanes was prepared in good yields and high regioselectivity. The observed reactivity was shown to be in agreement with Mayr's nucleophilicity and electrophilicity scales.     

General and highly efficient fluorinated-N-heterocyclic carbene–based catalysts for the palladium-catalyzed Suzuki–Miyaura reaction

A general and highly efficient trifluoromethylated-N-heterocyclic carbene (NHC)-based catalyst for the palladium-catalyzed Suzuki–Miyaura reaction was reported. In the presence of the catalyst, reactions of non-activated aryl chlorides and triflates with aryl boronic acids occurred at room temperature with good to excellent yields (63–98%). In addition, catalysts generated from a combination of Pd(OAc)₂/imidazolium salt 6a is not only effective for the coupling of heteroaryl boronic acid with aryl halides and heteroaryl halides, but also efficient for coupling of other heteroaryl halides and heteroaryl boronic acids. Finally, the catalyst is highly effective for Suzuki–Miyaura reaction of aryl bromides and chlorides with 0.01–0.1 mol % loading if the temperature was raised at refluxed THF/H₂O.     

Phosphosulfonic acid‐catalyzed green synthesis and bioassay of α‐aryl‐α′‐1,3,4‐thiadiazolyl aminophosphonates

A series of new α‐aminophosphonates containing 1,3,4‐thiadiazole moiety (4a–l) were synthesized via a simple, efficient, and one‐pot three‐component Kabachnik–Fields reaction of 2‐amino‐5‐ethyl‐1,3,4‐thiadiazole with various aryl/heteroaryl aldehydes and diethylphosphite under solvent‐free microwave irradiation conditions using phosphosulfonic acid, as a reusable and heterogeneous solid acid catalyst. All the title compounds were screened for radical scavenging activity by DPPH and H₂O₂ methods, and antimicrobial activity against bacteria (Gram‐positive and Gram‐negative) and fungi using the disc diffusion technique. They exhibited potent in vitro antioxidant and moderate antimicrobial activity.     

Simultaneous saccharification and cofermentation of peracetic acid-pretreated biomass

Previous work in our laboratories has demonstrated the effectiveness of peracetic acid for improving enzymatic digestibility of lignocellulosic materials. The use of dilute alkali solutions as a pre-pretreatment prior to peracetic acid lignin oxidation increased carbohydrate hydrolysis yields in a synergistic as opposed to additive manner. Deacetylation of xylan is easily achieved using dilute alkali solutions under mild conditions. In this article, we evaluate the effectiveness of peracetic acid combined with an alkaline pre-pretreatment through simulataneous saccharification and cofermentation (SSCF) of pretreated hybrid poplar wood and sugar can ebagasse. Respective ethanol yields of 92.8 and 91.9% of theoretical are achieved using 6% NaOH/15% peracetic acid-pretreated substrates and recombinant Zymomonas mobilis CP4/p ZB5. Reduction of acetyl groups of the lignocellulosic materials is demonstrated following alkaline pre-pretreatments. Such processing may be helpful in reducing peracetic acid requirements. The influence of deacetylation is more significant in combined pretreatments using lower peracetic acid loadings.     

One-pot copper-catalyzed synthesis of N-functionalized pyrazoles from boronic acids

A straight-forward route to prepare a diverse set of N-aryl pyrazoles via a one-pot copper-catalyzed boronic acid coupling and cyclization protocol is presented. A variety of aryl and heteroaryl N-functionalized pyrazoles not easily accessible by other means were formed in good yield from readily available boronic acid precursors in an operationally simple procedure.     

Microwave-assisted palladium-catalysed carbonylations of aryl and heteroaryl halides with sulfamide nucleophiles utilising a solid CO source

Mo(CO)₆ acts as a source of carbon monoxide for the palladium-catalysed, microwave-assisted, carbonylative coupling of aryl or heteroaryl halides with sulfamide nucleophiles to yield aryl and heteroaryl acyl sulfamides.     

Tetraphosphine/palladium‐catalyzed Suzuki–Miyaura coupling of heteroaryl halides with 3‐pyridine‐ and 3‐thiopheneboronic acid: an efficient catalyst for the formation of biheteroaryls

An easily prepared tetraphosphine N,N,N′,N′‐tetra(diphenylphosphinomethyl)‐1,2‐ethylenediamine (L1) associated with [Pd(η³‐C₃H₅)Cl]₂ affords an efficient catalyst for Suzuki–Miyaura coupling of 3‐pyridineboronic acid with heteroaryl bromides. Reaction could be performed with as little as 0.02 mol% catalyst and a high turnover number of 2500 is obtained. A wide range of substrates is investigated with satisfactory yields, and good compatibility with aminogroup‐substituted pyridines and unprotected indole is exhibited. This protocol can also be applied successfully to the reaction of heteroaryl bromides with 3‐thiopheneboronic acid. This Pd‐tetraphosphine catalyst efficiently restrains the poisoning effect from heteroaryls, and shows good stability and longevity. Copyright © 2013 John Wiley & Sons, Ltd.     

Depolymerization and ionic conductivity of enzymatically deproteinized natural rubber having epoxy group

Preparation of liquid epoxidized natural rubber (ENR) was made by oxidative depolymerization of ENR in latex stage without loss of epoxy group. Epoxidation of fresh natural rubber latex, which was purified by deproteinization with proteolytic enzyme and surfactant, was carried out with freshly prepared peracetic acid. The glass transition temperature (T_g) and gel content of the rubbers increased after the epoxidation, both of which were dependent upon an amount of peracetic acid. The gel content was significantly reduced by oxidative depolymerization of the rubber with (NH₄)₂S₂O₈ in the presence of propanal. The resulting liquid epoxidized rubber (M_n≈10⁴) was found to have well-defined terminal groups, i.e. aldehyde groups and α-β unsaturated carbonyl groups. The novel rubber was applied to transport Li⁺ as an ionic conducting medium, that is, solid polymer electrolyte.     

Facile N-formylation of amines using Lewis acids as novel catalysts

Alky, aryl, and heteroaryl amines were found to react efficiently with formic acid under Lewis acid catalysis giving N-formyl derivatives in high yields. A study of ZnCl₂-catalyzed N-formylation of a variety of amines using formic acid as formylating agent is described.     

Regioselective synthesis of Δ3-butenolides via oxidation of 2-trimethylsilylfurans

5-Alkyl-2-trimethylsilylfurans, easily accessible via successive alkylation and silylation of furan, undergo oxidation cleanly with peracetic acid to afford the corresponding Δ³-butenolides in good yields.     

Silica chloride (SiO2-Cl) catalyzed one pot synthesis of 2,3-disubstituted-thiazolidin-4-one

Abstract

In this paper, we report one-pot, three-component cyclo condensation of an aldehyde, an amine and thioglycolic acid to form 2,3-disubstituted-thiazolidin-4-one by using supported protic acid (Silica Chloride: SiO₂-Cl) catalyst. The catalyst SiO₂-Cl is compatible with a variety of aldehydes (aryl/heteroaryl) and the aromatic amines affording 2,3-disubstituted-thiazolidin-4-one analogs in 72–89% yields. Moreover, the supported catalyst was recycled several times without significant loss of catalytical activity