Traceless polymer-supported divergent synthesis of quinoxalinones by microwave irradiation

A novel protocol for rapid assemble of quinoxalinones framework has been demonstrated. This method incorporated with soluble polymer support provides a convenient approach for diversification of heterocyclic compounds and for easy purification via facile precipitation from reaction matrix. The key transformation of this study involves in situ reduction of aromatic nitro compound, tandem lactamization concomitant with traceless cleavage of the polymer support under microwave irradiation in a one-pot fashion. Moreover, forward synthetic routes were introduced to maximize complexity of the master intermediate on which further chemical elaboration was applied. The strategy is envisaged to apply for establishment of drug-like small-molecule libraries for high-throughput screening.     

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.     

Soluble polymer-supported convergent parallel library synthesis

Soluble polymer-supported convergent synthesis has for the first time been successfully exploited for parallel library synthesis; sub-libraries of tripeptide iodoarenes and arylboronic acids reacted smoothly in a multipolymer PdII-catalyzed Suzuki coupling reaction to generate a library of bisaryl-linked hexapeptides.     

Solvent-and catalyst-free synthesis of dihydropyrimidinthiones in one-pot under focused microwave irradiation conditions

Fifteen dihydropyrimidinthiones have been synthesized by microwave-assisted Biginelli reactions without any solvent or catalyst. The advantages of this novel protocol include the excellent yield, operational simplicity, short time and the avoidance of the use of organic solvents and catalysts.     

An efficient synthesis of substituted cytosines and purines under focused microwave irradiation

A rapid nucleophilic displacement reaction of 6-chloropurine, 2-amino-6-chloropurine and 5-bromocytosine with various nucleophiles under focused microwave irradiation is described. Using this method, the desired products were obtained with the yields up to 99% in a short reaction time.     

Mercury chloride assisted cyclization toward benzimidazoles by focused microwave irradiation

An efficient, microwave-assisted method for the mercury chloride mediated synthesis of 1,2-disubstituted benzimidazoles has been developed. Biologically interesting benzimidazoles were readily assembled utilizing S_NAr reactions, reduction, and followed with mercury(II) mediated cyclization under microwave irradiation. The desired products were then liberated from the soluble matrix in excellent yield and purity after cleavage.     

Combinatorial synthesis of biheterocyclic benzimidazoles by microwave irradiation

Liquid phasel synthesis of biheterocyclic benzimidazoles by controlled microwave irradiation was investigated. Polymer immobilized o-phenylenediamines was synthesized under microwave irradiation. The resulting PEG bound diamines was N-acylated with 4-fluoro-3-nitrobenzoic acid selectively in primary aromatic amino moiety. Nucleophilic aromatic substitution of amide was performed with various amines then cyclized to form the first benzimidazole scaffold in acidic condition. Successive reduction, cyclization with isothiocyanates yielded 5-(benzimidazol-2-yl)benzimidazoles. The desired products were released from the polymer support to afford the tri-substituted bis-benzimidazoles in good yields and purity.     

Parallel synthesis of amino bis-benzimidazoles by multistep microwave irradiation

A multistep liquid phase synthesis of specifically functionalized bis-benzimidazoles is presented by the application of single-mode microwave irradiation technique. The sustained solubilizing power and stability of the PEG-ester derived from the commercially available 4-fluoro-3-nitrobenzoic acid has been successfully carried through 10 steps involving ipso-S_NAr reaction, neutral reduction and acid cyclization. All the steps in this synthetic sequence were assisted by microwave (MW) irradiation. The polymer support was cleaved to release the final head to tail bisbenzimidazoles in an efficient process.     

Liquid phase synthesis of chiral quinoxalinones by microwave irradiation

Single mode microwave-assisted combinatorial synthesis of biologically interesting quinoxalinones is described. Chiral libraries of quinoxalinone were readily assembled utilizing S_NAr reactions, reduction and followed with concomitant cyclization under microwave irradiation. Enantiomeric 1,2,3,4-tetrahydroquinoxalinones were isolated in excellent yield and purity after cleavage.     

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.     

Synthesis and modification of oxetane based oligomers with 3-ethoxypropylamine by focused microwave irradiation

Synthesis of oligomers was achieved via condensation of several bisphenol sodium salts in water with 3,3^′-bis(chloromethyl)oxetane in nitrobenzene under phase transfer catalysis with tetrabutyl ammonium bromide. All proceedings were developed both by classical and under focused microwave irradiation with complete experimental parameters control. The rigid oxetane chain was then opened partially with 3-ethoxypropylamine in order to generate some specific properties. Higher substitution was obtained by microwave activation in the presence of the zinc chloride which is well known to react as microwave absorber.     

微波法快速合成环金属铂配合物磷光发光材料

采用微波合成法合成了一系列新的含不同β-二酮的环金属铂配合物.在微波反应条件下,反应时间从32h减少到30min左右.同时,对环金属铂配合物的吸收和发射光谱、热稳定性,磷光寿命的影响进行了讨论.     

Soluble polymer-supported catalysts containing azo dyes

[structure: see text] Azo benzene derivatives were incorporated into soluble polymer-bound catalysts by two different approaches. The first was to attach the dye to the polymer-bound catalysts, using the dye as an innocent spectator to study the phase preference, concentration, and recoverability of a catalyst. The second approach used an azo dye as a ligand to form an effective soluble polymer-bound Pd(II) catalyst for Heck reactions.     

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.     

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。     

Rapid and efficient synthesis of 1,2,4-oxadiazoles utilizing polymer-supported reagents under microwave heating

1,2,4-Oxadiazoles can be rapidly and efficiently synthesized from a variety of readily available carboxylic acids and amidoximes using either method A or method B. The use of commercially available polymer-supported reagents combined with microwave heating resulted in high yields and purities of the product 1,2,4-oxadiazoles in an expeditious manner. [structure: see text]     

Light fluorous-tagged traceless one-pot synthesis of benzimidazoles facilitated by microwave irradiation

A novel protocol for rapid assemble of benzimidazole framework has been demonstrated. This method incorporated with light fluorous-tag provides a convenient method for diversification of benzimidazoles and for easy purification via fluorous solid-phase extraction (F-SPE) in a parallel manner. The key transformation of this study involves in situ reduction of aromatic nitro compound, amide formation, cyclization and aromatization promoted by microwave irradiation in a one-pot fashion. The strategy is envisaged to be applied for the establishment of drug-like small molecule libraries for high throughput screening.     

Solvent-free synthesis of functionalized flavones under microwave irradiation

[reaction: see text] Eco-friendly direct solvent-free synthesis of flavones is achieved by microwave irradiation of phloroglucinol and beta-ketoesters. Heating with microwaves versus under classical conditions was shown to be higher yielding, cleaner, and faster. The reaction goes through a cycloaddition of an alpha-oxo ketene intermediate followed by an uncatalyzed thermal Fries rearrangement.     

An improved synthesis of alpha-carbolines under microwave irradiation

[reaction: see text]. Alpha-carbolines are interesting core structures for designing DNA-interacting small molecules. However, these compounds are not commercially available and their synthetic methods are low yielding or time consuming. The shortest synthetic route, the modified Graebe-Ullmann reaction, has been optimized by using microwave heating in four different types of apparatus to give shorter reaction times and enhanced yields. Optimized conditions enabled the preparation of a small library of alpha-carbolines.