Microwave-assisted aminolysis of vinylepoxides

Di- and trisubstituted vinylepoxides in NH₄OH were subjected to microwave irradiation affording the corresponding vicinal aminoalcohols in high yields. The reaction is stereospecific and highly regioselective for addition at the allylic carbon.     

One-pot microwave-assisted substitution of a glucuronan trisaccharide

Substitution of a glucuronic acid trisaccharide was easily performed in one step under microwave irradiation, affording a product resulting from simultaneous glycosylation, esterification and a butyl ether formation.     

Stereoconservative Negishi arylation and alkynylation as an efficient approach to enantiopure 2,2'-diarylated 1,1'-binaphthyls

Negishi arylation and alkynylation of easily synthesized chiral 2,2'-diodo-1,1'-binaphthyl rapidly proceeds in refluxing THF utilizing controlled microwave irradiation, affording enantiopure 2,2'-diarylated 1,1'-binaphthyls in good to excellent yields.     

New environmentally-friendly solvent-free synthesis of imines using calcium oxide under microwave irradiation

Condensation of structurally diverse aldehydes including heterocyclic aldehydes, like furfural, with various amines in the presence of calcium oxide affording the corresponding imines in solvent-free conditions in good to excellent yields under microwave irradiation is described. A comparative study has been done under thermal conditions. The synergy between dry media and microwave irradiation in this reaction is evaluated by condensing less electrophilic aldehydes with poorly nucleophilic amines. The main advantages of this environmentally friendly protocol are the use of the non-toxic and inexpensive reagent calcium oxide and the considerable rate enhancement in comparison with a thermal reaction.     

Microwave assisted sulfopropylation of N-heterocycles using 1,3-propane sultone

Dramatic rate acceleration was observed for N-sulfopropylation of heterocyclic compounds (1a-h) using 1,3-propane sultone(2) under microwave irradiation affording the N-sulfopropylated compounds (3a-h) in 68–95% yield.     

Synthesis of 1-alkyl-4-imidazolecarboxylates: a catch and release strategy

The novel alkyl N-methyl-N-polystyreneamino-2-isocyanoacrylate was used for the synthesis of 1-substituted imidazole-4-carboxylates utilizing a "catch and release" methodology. The reactions were performed under microwave irradiation, affording the title compounds in both high yields and chemical purity directly to solution, from the solid phase support.     

Sequential one-pot ruthenium-catalyzed azide-alkyne cycloaddition from primary alkyl halides and sodium azide

An experimentally simple sequential one-pot RuAAC reaction, affording 1,5-disubstituted 1H-1,2,3-triazoles in good to excellent yields starting from an alkyl halide, sodium azide, and an alkyne, is reported. The organic azide is formed in situ by treating the primary alkyl halide with sodium azide in DMA under microwave heating. Subsequent addition of [RuClCp*(PPh(3))(2)] and the alkyne yielded the desired cycloaddition product after further microwave irradiation.     

A new,one-pot,multicomponent synthesis of 5-aza-9-deaza-adenines under microwave irradiation

A new, practical, three-component method for the synthesis of 5-aza-9-deaza-adenines is developed. Aminopyrazoles react in a one-pot fashion with triethyl orthoformate and cyanamide under microwave irradiation affording 5-aza-9-deaza-adenines in good yields and high purity. The main advantages of this method are the operational simplicity, accessibility, and high efficiency.     

Reaction of substituted furan-2-carboxaldehydes and furo[b]pyrrole type aldehydes with hippuric acid

4-Heteroarylidene-2-phenyl-1,3-oxazol-5(4H)-ones were prepared by reactions of hippuric acid with substituted furan-2-carboxaldehydes or furo[b]pyrrole type aldehydes. The reactivity of various furan-2-carboxaldehyde derivatives in this reaction is discussed. The effect of microwave irradiation on some condensation reactions was compared with "classical" conditions. The results show that microwave irradiation shortens the reaction times while affording comparable yields. Elementary analysis, UV, IR and 1D NMR proved the structure of new synthesised compounds. 2D NMR spectroscopic measurements confirmed that the configuration at the carbon-carbon double bond corresponds to the pure E isomers of the products.     

微波辐射固相合成4-三氟甲基-7-羟基-6-氯香豆素

分别以无水氯化锌、对甲苯磺酸为催化剂,采用微波辐射法,在无溶剂条件下由4-氯间苯二酚与三氟乙酰乙酸乙酯缩合制备标题化合物;优化了反应条件.结果表明,在微波辐射下,无水氯化锌对该反应有较好的催化活性,相应的4-三氟甲基-7-羟基-6-氯香豆素的产率可达73.0%.优化的反应条件为:4-氯间苯二酚、三氟乙酰乙酸乙酯和无水ZnCl2的摩尔比为1∶1.1∶0.9,微波辐射功率800W,辐射时间20min,反应温度85℃.     

La(OTf)3 catalyzed synthesis of α-aryl tetrasubstituted pyrroles through [4+1] annulation under microwave irradiation

A La(OTf)₃ catalyzed synthesis of tetrasubstituted pyrroles under microwave irradiation has been developed affording various α-aryl tetrasubstituted pyrroles in acceptable to good yields (36–82% yield) through condensation/alkyne azacyclization/isomerization sequence. Functionalized α-aryl pentasubstituted pyrroles could be prepared from tetrasubstituted pyrroles through easy transformations.     

微波辅助合成双1,2,4-三嗪化合物及其荧光特性研究

以联苯甲酰、二甲酰肼为原料, 采用微波技术合成了5个双1,2,4-三嗪化合物3, 产率72%～85%, 利用元素分析、MS, IR, ¹H NMR和荧光光谱对其结构进行了表征, 并研究了金属离子对化合物3a的荧光性质的影响. 结果表明, 微波合成具有缩短反应时间、提高产率的优点; Cu^2＋, Ni^2＋等金属离子对化合物3a产生明显的荧光猝灭作用.     

A "catch and release" strategy for the parallel synthesis of 2,4,5-trisubstituted pyrimidines

A resin capture and release strategy for making a combinatorial array of 2,4,5-trisubstituted pyrimidines is demonstrated by capturing beta-ketoesters and beta-ketoamides on a solid-supported piperazine. Through a cyclocondensation reaction, the solid-supported enaminone is reacted with several guanidines under heating or microwave irradiation affording the corresponding pyrimidines in good yield and chemical purity directly on solution. After this final step, the support can be effectively recycled.     

Microwave-assisted synthesis of resorcin[4]arene and pyrogallol[4]arene macrocycles

A series of resorcin[4]arene and pyrogallol[4]arene macrocycles have been synthesized efficiently within 5 min, affording crystalline products suitable for single crystal X-ray diffraction, utilising microwave irradiation in a ‘one-pot’ reaction whilst controlling the selective formation of the rccc cone stereoisomer.     

Glycerol as a recyclable solvent in a microwave-assisted synthesis of disulfides

Abstract

We present here a clean and fast synthesis of organic disulfides starting from thiols using glycerol as solvent under microwave irradiation. This efficient method is general for aromatic, aliphatic, and functionalized thiols, affording the corresponding disulfides in good to excellent yields after easy work up. Glycerol can be easily recovered and utilized for further oxidation reactions.     

A combination of water and microwave irradiation promotes the catalyst-free addition of pyrroles and indoles to nitroalkenes

A combination of water and microwave irradiation was used for the first time to perform a catalyst-free nitro-Michael addition of pyrroles and indoles. Under superheated conditions, the water trends to ionize by changing its chemical and physical properties. Therefore, we performed a new green-protocol using the water either as environmentally no harm solvent or as catalyst. The reaction success is independent from the kind of pyrrole, indole or nitroalkenes rapidly affording the corresponding adducts and giving excellent yields.     

Microwave-Induced Solvent-free Synthesis of β-Keto Esters Using Montmorillonite KSF and K10 Clays as Efficient and Recyclable Heterogeneous Solid Acids

Montmorillonite KSF and K10 clays catalyzed effectively the reaction of methyl diazoacetate with various aldehydes using microwave irradiation under solvent-free conditions affording the corresponding β-keto esters in good yields and short reaction time. The present method is an improvement for the previous known synthetic methods and has many obvious advantages compared to them including the high efficiency, generality, high yields, operational simplicity, environmental benignity, and possibility of recycling the natural solid clays.     

Suzuki cross‐coupling reactions of aryl chlorides using [Cl2Pd(COD)]/piperazine derivative under microwave conditions

A new strategy to significantly improve the efficiency of Suzuki reactions was achieved under microwave irradiation. [Cl₂Pd(COD)]/piperazine derivative 1 catalyzed aryl chlorides with phenylboronic acid in methanol (50%) affording excellent yields under aerobic conditions. Application of this strategy to the synthesis of liquid crystal material is also described. Copyright © 2011 John Wiley & Sons, Ltd.     

Modular CeCl3·7H2O-catalyzed multi-component synthesis of 1,2,3,4-tetrasubstituted pyrroles under microwave irradiation and their further trichloroisocyanuric acid-mediated conversion into 5-sulfenylpyrrole derivatives

A modular, multicomponent synthesis of 1,2,3,4-tetrasubstituted pyrroles promoted by the inexpensive CeCl₃·7H₂O, is reported. The reaction was carried out under microwave irradiation, affording good yields of products in short time. Scope and limitations were explored and a plausible reaction mechanism is discussed. The resulting heterocycles were smoothly and efficiently converted into their corresponding 5-arylsulfenyl derivatives by reaction with diaryl disulfides and trichloroisocyanuric acid in EtOAc.     

Atom-Economic Synthesis of Functionalized Octahydroacridines from Citronellal or 3-(Phenylthio)-citronellal

Here we present a simple, solvent-free, one-pot, hetero-Diels–Alder reaction of (R)-citronellal or 3-(phenylthio)-citronellal with arylamines using solid-supported catalyst (SiO₂/ZnCl₂). This general, efficient, and improved method is selective, affording preferentially new trans-fused 3-(phenylthio)-octahydroacridines (S-OHAs) in good yields. The use of microwave irradiation facilitates the procedure and accelerates the reaction.