无溶剂微波辅助合成醚类化合物的工艺探讨

与传统加热方法相比,通过体系内部分子运动摩擦产热的微波辐射方法可催化化学反应,缩短反应时间,提高转化率和收率.传统的加热方法需要数十小时,甚至几天的反应.     

Efficient Acylation and One-Pot Synthesis of Dehydroandrographolide Succinate on a Large Scale Assisted with Microwave Radiation

A rapid and convenient method for acylation and large-scale synthesis of dehydroandrographolide succinate has been developed under microwave irradiation. It is a one-pot condensation and is compatible with dehydration and rearrangement of double bond in mild reaction conditions with good yield, high purity (up to 99.8%), time-savings, few pollutants and low cost. In addition, a number of acylation derivatives were synthesized under microwave irradiation.     

SYNTHESIS OF AMINONAPHTHALENE DERIVATIVES USING THE BUCHERER REACTION UNDER MICROWAVE IRRADIATION

A very simple and efficient method to prepare aminonaphthalene derivatives in good yield using the Bucherer reaction under microwave irradiation in a closed vessel is described. A reaction time of 30min at 150 Watts of microwave power was established as the optimum irradiation conditions when approximately 2 g of the initial hydroxynaphthalene was used in the synthesis.     

Microwave-accelerated derivatization processes for the determination of phenolic acids by gas chromatography-mass spectrometry

A rapid method for the derivatization of phenolic antioxidants using microwave irradiation has been developed. Six antioxidatively active phenolic components of wines and fruits, namely gallic acid, gentisic acid, vanillic acid, caffeic acid, ferulic acid and p-coumaric acid were used in the model study. The solution of phenolic acids was evaporated to dryness on a rotary evaporator followed by further drying under microwave irradiation (600 W, 30 s). The resultant residue was dissolved in pyridene and treated with bis(trimethylsilyl)acetamide while irradiated by microwave using high power for 30 s. Controlled reaction was carried out employing bis(trimethylsilyl)trifluoroacetamide under conventional heating for 30 min. The trimethylsilyl derivatives were identified and quantified on a gas chromatography/mass selective detector. The mass spectral fragmentation patterns of the derivatives obtained by microwave irradiation were identical to those prepared by heating. The yields of microwave-assisted silylation were comparable to those from conventional heating. The rsd were less than 8% for six replicates. The linearity in wine matrix was nearly perfect. This method is a useful protocol to examine the phenolic constituents in wines and agricultural products.     

Facile microwave-assisted synthesis of thioformamides from isocyanides and carbon disulfide

A new, fast, solvent-free and efficient method is provided to prepare thioformamides by reacting isocyanides derivatives, carbon disulfide and benzylamine under microwave irradiation.     

Microwave-Assisted Synthesis of Some Bi- and Tricyclic Pyrimidine Derivatives

Pyrimidine derivatives 4a-4c was prepared by a Biginelli cyclocondensation of g -ketoesters, aryl aldehydes, and thiourea derivatives under microwave irradiation. A simple and fast synthesis of bicyclic pyrimidine derivatives 6a-6c was performed by microwave-assisted reaction of 4a-4c with bromomalononitrile ( 5 ). Reaction of bicyclic pyrimidines 6a-6c with HCO 2 H and HONH 3 Cl under microwave irradiation gave tricyclic pyrimidines 7a-7c and 8a-8c respectively.     

Efficient and Novel Synthesis of Benzoxazole Derivatives in the Presence of Zinc Dust Under Solvent-Free Conditions

A mild and efficient method has been developed for the synthesis of 2-cyclic amine-substituted benzoxazole derivatives using zinc dust under microwave irradiation in the absence of solvent is described. A comparative study was performed under conventional and microwave heating conditions. Zinc dust can be reused several times after reactivation. The significant feature of this method is the isolation of the pure product by simple workup in a short reaction time with high purity.     

BF3·nano SiO2 as a catalytic system for one-pot green synthesis of pyrophthalone derivatives under microwave conditions: 1st Nano Update

The expeditious and solvent-free approach that involves the exposure of neat reactants to microwave (MW) irradiation in conjunction with the use of supported catalysts was described. A simple one-pot and green reaction of methylpyridine derivatives and phthalic anhydride derivatives on the surface of a nano silica gel impregnated with BF₃ as solid supported catalysts under microwave irradiation without any solvent according to green chemistry was developed. The salient features of these high yield protocols are the enhanced reaction rates, greater selectivity and the experimental ease of manipulation.     

Microwave assisted solvent free amination of halo-(pyridine or pyrimidine) without transition metal catalyst

A solvent free direct amination of halo-(pyridine or pyrimidine) has been developed in good to high yields under computer-controlled microwave irradiation without transition metal catalyst. This reaction is a solvent and metal free, useful method for coupling of halo-(pyridine or pyrimidine) with pyrrolidine and piperidine derivatives by nucleophilic aromatic substitution (S_NAr).     

Silica sulfuric acid as an efficient catalyst for the Friedländer quinoline synthesis from simple ketones and ortho-aminoaryl ketones under microwave irradiation

The synthesis of quinoline derivatives via Friedländer method from ortho-aminoaryl ketones in the presence of a catalytic amount of silica sulfuric acid (SSA) under solvent-free condition and microwave irradiation was described. A good range of simple ketones such as cyclohexanone and deoxybenzoin were used.     

Microwave-assisted synthesis of 2-aminothiophene-3-carboxylic acid derivatives, 3H-thieno[2,3-d]pyrimidin-4-one and 4-chlorothieno[2,3-d]pyrimidine

A two-minute microwave irradiation allowed the synthesis of several 2-aminothiophene-3-carboxylic acid derivatives. Their efficient transformation to thieno[2,3-d]pyrimidin-4-one and the corresponding 4-chloro derivative is also reported under microwave irradiation.     

Facile and efficient synthesis of a new class of bis(3′-indolyl)pyridine derivatives via one-pot multicomponent reactions

A series of 4-aryl-3,5-dicyano-2,6-di(3′-indolyl)pyridine derivatives were synthesized via a one-pot multicomponent reaction of aromatic aldehydes, 3-cyanoacetyl indoles, and ammonium acetate under microwave irradiation. Particularly valuable features of this method include high yields of products, broad substrate scope, short reaction time, and straightforward procedure.     

One‐Pot Microwave‐Assisted Synthesis of Benzopyrano[2,3‐c]pyrazol‐3‐one Derivatives

A convenient one‐pot microwave‐assisted synthesis of Benzopyrano[2,3‐c]pyrazol‐3‐one derivatives was developed, where Knoevenagel condensation and hydrazinolysis reactions were continuously performed under microwave irradiation without separation and purification of the intermediates until the last cyclocondensation reaction except the substrates addition. The one‐pot procedure exhibited shorter reaction times and higher yields (25–55%) of the objects than the conventional heating method.     

A novel method for the separation of bis(alpha-hydroxyalkyl)phosphinic acid diastereoisomers via formation of novel cyclic phosphinic acids

The reaction of aromatic and aliphatic aldehydes with hypophosphorus acid under microwave irradiation was examined. The reaction gave a mixture of a racemic pair of bis(alpha-hydroxyalkyl)phosphinic acids and acetal derivatives from the corresponding bis(alpha-hydroxyalkyl)phosphinic acids of meso-stereochemistry in good yield. The difference in solubility in organic solvents due to polarity allowed us to readily separate these compounds. This method constitutes an easy, rapid, and good-yielding preparation and separation of bis(alpha-hydroxyalkyl) phosphinic acid diastereoisomers from simple starting materials using microwave irradiation.     

An efficient and rapid synthesis of β-carboxamide derivatives using 2,2-dimethyl-2H,4H-1,3-dioxin-4-ones by microwave irradiation

A general, efficient and rapid method for the synthesis of various β-carboxamide derivatives using microwave irradiation is described. Excellent isolated yields were obtained in very short reaction times when conventional heating was replaced by microwave irradiation.     

2-氨基噻唑5位的羟甲基化和胺甲基化

采用微波法、封管加热以及酯基还原三种方法,在2-氨基噻唑衍生物的5位引入羟甲基,得到一系列新的5位羟甲基取代的新衍生物.并将三种方法进行对比,结果表明,封管加热对底物热稳定性要求苛刻,反应时间长,反应液杂,反应收率低.酯基还原的方法需在合成噻唑前引入酯基后还原,路线长,且收率低.采用微波法,反应时间短,转化率高,反应液副产物少,收率明显高于其他两种合成方法.同时报道了用NaH作碱制得氰基酯钠盐,再经关怀关环、还原得到一系列5位为氨甲基的噻唑新衍生物.     

Aromatization of Various 1,4‐Dihydropyridines by Tetrabutylphosphonium Dichromate (TBPDC) under Conventional Heating and Microwave Irradiation

Tetrabutylphosphonium dichromate (TBPDC) has been found an efficient oxidizing agent for the aromatization of various 1,4‐dihydropyridines to their pyridine derivatives in refluxing acetonitrile and also under microwave irradiation. Short reaction times and clean workup are the advantages of this method.     

Microwave assisted one pot synthesis of 2-ethylamino benzimidazole,benzoxazole and benzothiazole derivatives

A rapid and efficient one-pot method for the synthesis of 2-ethylamino benzimidazole, benzoxazole, and benzothiazole derivatives has been described. The reaction of o-phenylenediamines or o-aminophenols or 2-mercaptoanilines with EDC.HCl under microwave irradiation afforded the corresponding 2-ethylamino benzimidazole, benzoxazole and benzothiazole derivatives in excellent yields.     

An efficient protocol for the solid-phase synthesis of glycopeptides under microwave irradiation

A standardized and smooth protocol for solid-phase glycopeptides synthesis under microwave irradiation was developed. Double activation system was proved to allow for highly efficient coupling of Tn-Ser/Thr and bulky core 2-Ser/Thr derivatives. Versatility and robustness of the present strategy was demonstrated by constructing a Mucine-1 (MUC1) fragment and glycosylated fragments of tau protein. The success of this approach relies on the combination of microwave energy, a resin consisting totally of polyethylene glycol, a low excess of sugar amino acid and the "double activation" method.     

Preparation and Characterization of Quaternized Chitosan Under Microwave Irradiation

For the first time, N-(2-hydroxyl) propyl-3-trimethyl ammonium chitosan chloride (HTCC) was prepared through a fast, easy and efficient method with the assistance of microwave irradiation, and the quaternized chitosan was also degraded via the microwave irradiation. A comparative study was performed by using the conventional heating method to prepare HTCC. The structure and property of the quaternized chitosan obtained by these two methods were characterized by GPC, XRD, FTIR, NMR, TG and elemental analysis. It was shown that quaternized chitosan was successfully prepared within 50 min via microwave irradiation method, while a much longer time of 6–7 h was needed with the conventional heating method. The substitutions both occurred on the C2 position of chitosan with the two different methods, and their HTCC products had weight average similar molecular weight (Mw), structure and thermal stability. The HTCC prepared by the microwave irradiation method had a little lower degree of substitution (DS) than those prepared via conventional heating with the same mole ratio (6:1) of the intermediate to chitosan. The degradation study showed that the Mw of HTCC decreased rapidly from 4.6 × 10⁵ to 1.1 × 10⁵ in 1 h under microwave irradiation, while it only decreased from 4.6 × 10⁵ to 2.1 × 10⁵in 1 h through conventional heating degradation. These results revealed that microwave irradiation is a more efficient and environment-friendly way to obtain the water-soluble chitosan derivatives and their degraded products.