Highly selective N-allylation of anilines under microwave irradiation

An easy and rapid procedure for the preparation of a variety of mono- and bis-allylated anilines via the reaction of allyl bromide with a wide range of anilines under microwave irradiation is described. This approach allows use of mild conditions and short reaction times to give high selectivities and excellent yields.     

Ionic liquid promoted selective debromination of α-bromoketones under microwave irradiation

The debromination of α-bromoketones with an easily accessible ionic liquid, 1-methyl-3-pentylimidazolium tetrafluoroborate, [pmIm]BF₄ under microwave irradiation has been investigated. By controlling the reaction time gem-α-dibromoketones are selectively debrominated to either monobromo or debromoketones. The α-monobromo- and α-monoiodoketones are dehalogenated while the corresponding chloroketones remain inert. The activated vic-bromoacetates are converted to the corresponding (E)-alkenes by the same procedure. These reactions do not require any organic solvent, any metal or any conventional reducing agent. The ionic liquid works here as catalyst as well as reaction medium and is recycled without any appreciable loss of its catalytic efficiency.     

Traceless synthesis of hydantoin by focused microwave irradiation

An efficient, microwave-assisted method for the liquid-phase combinatorial synthesis of 1,3-disubstituted hydantoin has been developed. Chloroacetyl chloride was directly anchored to HO-PEG-OH and subsequently reacted with various primary amines in a microwave cavity. The PEG bound secondary amine coupled with isocyanates and concomitant cyclization-cleavage step occurred in mild basic conditions by microwave flash heating. The desired products were then liberated from the soluble matrix in modest yield and high purity.     

Solvent-free and catalyst-free method for the synthesis of 2,4,5-triarylimidazoles under microwave irradiation

A facile procedure for the synthesis of 2,4,5-triarylimidazoles is being reported starting from benzil, aromatic aldehyde and ammonium acetate. The reactions were carried out with catalyst-free, solvent-free and under microwave irradiation conditions in high yield (80–99%) with short time (3–5 min) and environmental benign, as well as convenient operation. The structures of the compounds have been confirmed on the basis of their IR, ¹H NMR, and/or ¹³C NMR, MS, and elemental analyzer.     

Microwave-assisted reactions： Three-component process for the synthesis of 2-amino-2-chromenes under microwave heating

2-Amino-2-chromenes are class of heterocycles that posses considerable interest as pigments,cosmetics,potential agrochemicals and being the main constituents of many natural products.Although,they are generally prepared either under conventional heating,benign reagents or very recently,a three component condensation in poly-ethylene glycol-water in the presence of nanosized magnesium oxide,most of these methods require prolonged reaction time,reagents in stoichiometric amounts and generate moderate yield...     

Catalyst-free and solvent-free method for the synthesis of quinoxalines under microwave irradiation

A facile procedure for the synthesis.of quinoxalines is being reported starting from benzil and 1,2-diaminobenzene. Thereactions were carried out catalyst-free, solvent-free and under microwave irradiation conditions in high yield (84-98%) with short time (3-6 rain) and environmental benign, as well as convenient operation. The structures of all the compounds have been confirmed on the basis of their IR, 1H NMR, and/or 13C NMR, mass spectral data.     

Fast synthesis of temperature-sensitive PNIPAAm hydrogels by microwave irradiation

A novel method, microwave irradiation synthesis, is proposed for the preparation of thermo-sensitive poly(N-isopropylacrylamide) (PNIPAAm) hydrogels. The PNIPAAm hydrogels were separately synthesized by using microwave irradiation method and water-bath heating method. Chemical groups, lower critical solution temperature (LCST) and surface morphology of these PNIPAAm hydrogels were characterized by FT-IR, DSC and SEM. Swelling ratios of the gels were measured gravimetrically in the temperature range from 10.0 to 60.0 °C. Results showed that (1) the use of microwave irradiation can greatly shorten the reaction time required for PNIPAAm hydrogel synthesis from several hours to several minutes in comparison with water-bath heating method, and obviously improve the yields of the PNIPAAm gels, which were up to 99% after a short reaction time; (2) SEM micrographs and textural measurement revealed that the gels synthesized using microwave irradiation had more porous structure, and their average pore sizes and specific surface areas were larger than those of the gels synthesized using water-bath heating method; and (3) the PNIPAAm hydrogels synthesized using microwave irradiation had much higher swelling ratios at 10.0 °C below the LCST, and had lower swelling ratio at 60.0 °C above the LCST compared to the hydrogels synthesized by water-bath method.     

A rapid and efficient synthesis of indoloquinolinone and its analogues under microwave irradiation

A rapid and efficient method was established for the synthesis of indoloquinolinone and its analogues using acid-promoted cyclization in the present of PPA. All the reactions were completed in good yields in lOmin under microwave irradiation.     

Facile and efficient synthesis of quinoline-4-carboxylic acids under microwave irradiation

<正>A facile and efficient method for the preparation of 2-non-substituted quinoline-4-carboxylic acids is described via the Pfitzinger reaction of isatins with sodium pyruvate following consequent decarboxylation under microwave irradiation.     

Multicomponent reactions for the synthesis of new 3′-indolyl substituted heterocycles under microwave irradiation

A series of polysubstituted (3′-indolyl)pyrazolo[3,4-b]pyridine and (3′-indolyl)benzo[h]quinoline derivatives were synthesized via one-pot multicomponent reactions of aldehydes, 3-cyanoacetyl indoles with 5-aminopyrazol or naphthylamine under microwave irradiation. Particularly valuable features of this method include high yields of products, broad substrate scope, short reaction time and straightforward procedure.     

Rapid synthesis of biodegradable poly(epsilon-caprolactone-co-p-dioxanone) random copolymers under microwave irradiation

<正>Biodegradable poly(epsilon-caprolactone-co-p-dioxanone)(PCDO) random copolymers have been synthesized by ring-opening polymerization of epsilon-caprolactone(CL) and p-dioxanone(PDO) under microwave irradiation.The effects of irradiation time and different CL/PDO molar feed ratios on the microwave-assisted ring-opening polymerization(MROP) of PCDO have been discussed.The resultant products were characterized by ~1H NMR,GPC and DSC.It was found that the polymerization was completed within 20 min at 140℃.In the presence of different CL/PDO molar feed ratios,the conversions of both monomers were kept relatively constant.DSC sturdy suggested that with increasing the content of PDO in the copolymers,the crystalline degree of the copolymers decreased gradually.It is believed to be a promising biodegradable material.     

水溶液中微波辅助下5-碘嘧啶类化合物的合成

5-碘嘧啶类衍生物具有显著的化学治疗活性和有机合成用途。碘苷(又名疱疹净)于1962年被美国FDA批准用于治疗疱疹病毒角膜炎,这是第一个抗单纯疱疹病毒药物[1]。以碘苷为中间体可以合成其它高效低毒的抗病毒药物[2]。另外,通过Suzuki、Sonogashira等金属催化偶联反应可以在5位引     

微波辐射下苯并(口恶)唑基吡啶的合成

含有苯并唑基的杂环化合物由于其特殊的生理活性而广泛用作医药、农药[1];因为具有较高的荧光量子产率,还可作为荧光增白剂、闪烁剂[2]等。现有合成方法反应时间长[3,4],而且需高温下进行。微波辐射下的有机合成具有反应时间短、产率高的特点[5]。本文在微波辐射条件下,利用邻氨基酚和吡啶羧酸的缩合反应,合成了2种苯并唑基取代吡啶。其优化反应条件为:多聚磷酸为催化剂,微波输出功率为500W,辐射时间4分钟。相比于常规反应,该条件下的反应速率是常规加热法反应速率的60倍且产率有所提高。合成路线如下:ppA=Polyphosphoricacid1　…     

Multicomponent reactions for synthesis of bioactive polyheterocyclic ring systems under controlled microwave irradiation

The multi-component reaction of 1-benzothiopyran-4-ones with heterocyclic amines and dimethylformamide-dimethylacetal (DMFDMA) in DMF at 150 °C under controlled microwave heating afforded novel poly-heterocyclic ring systems. Also, reaction of 3-dimethylaminomethylene-1-benzothiopyran-4-one with activemethylene derivatives was investigated. The structure of all products was established on the bases of spectral data and elemental analyses and alternative synthesis if possible. The prepared compounds were screened for their antitumor activity against HCT-116 “colon” cancer cell line and some derivatives showed promising activity.     

Efficient synthesis of 2,5-diketopiperazines using microwave assisted heating

In this study a general, efficient and environmentally benign solution phase synthesis of 2,5-diketopiperazines (DKPs) using microwave assisted heating in water is described. A series of 11 structurally different DKPs have been synthesized from dipeptide methyl esters. A range of common laboratory solvents have been tested as well as different reaction times and temperatures. Both classic thermal and microwave assisted heating have been investigated. Microwave assisted heating for 10 min using water as solvent proved, by far, to be the most efficient method of cyclization giving moderate to excellent yields (63-97%) of DKPs. In contrast to other published procedures, this method seems independent of the amino acid sequence.     

微波辐射下有效合成缩氨基硫脲类化合物

将肼基二硫代甲酸甲酯与相应的醛或酮在微波辐射下,经2~3.5m in反应得到化合物3-二取代甲(乙)撑肼基二硫代甲酸甲酯1,收率90~96%,然后将化合物1与胺在微波辐射下,经35~45m in反应得到目标化合物2~4,收率68~90%。微波辐射法比常规法显著的缩短了反应时间,提高了收率。共计合成目标化合物19个。以上化合物均经过熔点测定、质谱、红外光谱、核磁共振氢谱对其结构进行确证。     

An efficient one-pot, two-step synthesis of 4-substituted 1-heteroarylpiperazines under microwave irradiation conditions

A highly efficient one-pot, two-step microwave procedure has been developed for the synthesis of 4-substituted 1-heteroarylpiperazines. Microwave heating of heteroaryl chlorides with 1,4-diazabicyclo[2.2.2]octane (DABCO) at 160 °C for 15 min yielded 1-heteroaryl-4-(2-chloroethyl)piperazines, which could be further reacted with various nucleophiles, again under microwave irradiation conditions, to give an array of 4-substituted 1-heteroarylpiperazines in good to excellent yields.     

Effective synthesis of Tc tricarbonyl complexes by microwave heating

Technetium-99m (^99mTc) is one of the most frequently used nuclides for single-photon emission computed tomography (SPECT) imaging because of its radiochemical characteristics, such as gamma emission of suitable energy (141 keV) and adequate half-life (6.01 h). Although triaquatricarbonyl ^99mTc cation ([^99mTc(CO)₃(H₂O)₃]⁺) has several advantages as a ^99mTc-labeling agent, e.g., compact chelate size, chelate stability, and simplicity of preparation, its synthetic protocols should be improved. Because microwave heating is a convenient method for synthetic reactions, we studied the effect of microwave irradiation on the synthesis of ^99mTc tricarbonyl complexes. We found several factors beneficial for the preparation of nuclear medicines. In particular, microwave heating promoted one-pot syntheses of ^99mTc tricarbonyl chelates in a short time. In addition, the ^99mTc tricarbonyl complex could be obtained using low concentrations of ligands.     

Formation of monodispersed PVP-capped ZnS and CdS nanocrystals under microwave irradiation

Poly (N-vinyl-2-pyrrolidone) (PVP)-capped ZnS, CdS nanoparticles were prepared by a microwave method from Zn(Ac)₂ or Cd(Ac)₂ and thiourea in N,N-dimethylformamide (DMF) solution. The reaction process was monitored by the temporal evolution of the absorption spectrum. With PVP as stabilizer, monodispersed semiconductor nanoparticles, which showed high quantum size effect, have been obtained. Further study showed that the microwave irradiation could influence selectively the nucleation and growing rates of different semiconductor nanoparticles.     

Synthesis of diethers derived from furoin by phase transfer catalysis under microwave irradiation

A series of new diethers were obtained by alkylation of furoin under microwave irradiation (MWI) in phase transfer catalysis (PTC) conditions. The products of alkyl halides were synthesized in good yields (>75%) within a few minutes, and the products of dihalides were synthesized in fair yields (about 45%). The yields are dramatically improved compared to conventional heating under the same conditions, in spite of similar profiles of rising in temperature.