Microwave-assisted synthesis and heterocyclic functionalization of chromenopyridines on calixarene scaffold

A three-component one-pot condensation reaction of chroman-4-one with ethyl 2-cyanoacetate and various aldehydes in the presence of ammonium acetate afforded a series of 2-oxo-4-phenyl-1,5-dihydro-2H-chromeno[4,3-b]pyridine-3-carbonitrile. These heterocycles have been converted to chloropyridine derivatives and appended to macrocyclic calix[4]arene scaffold through aromatic nucleophilic substitution under microwave irradiation. In this study, the microwave-assisted functionalization of the lower rim of calix[4]arene has been considered the only appropriate tool because the conventional heating did not lead to any new product after 72 hours of heating under thermal condition.     

微波促进下4-乙炔基苯磺酰胺的“一锅法”合成

以3-(4-氯磺酰苯基)-2,3-二溴丙酸和氨水（2.2 eq）为原料,以 DMF为溶剂,经微波辐射25 s,磺酰胺化和脱溴脱羧反应可同步进行,立体选择性地合成中间体(Z)-4-(2-溴乙烯基)苯磺酰胺;该中间体不需分离,直接向反应体系中加入1,8-二氮杂环[5,4,0]十一烯-7 (DBU,2eq),再微波辐射1 min,“一锅法”得到4-乙炔基苯磺酰胺,并通过1H NMR和13C NMR和IR进行了表征,收率达70%。     

Microwave-assisted ketone-ketone rearrangement: an improved synthesis of 3-(4-alkoxyphenyl)-3- methylbutan-2-ones

[reaction: see text] A novel procedure for the preparation of 3-(4-alkoxyphenyl)-3-methylbutan-2-one in excellent yield is described via polymer-supported AlCl3-catalyzed rearrangement of 1-(4-ethoxyphenyl)-2,2-dimehtylpropan-1-one, followed by O-alkylation under microwave irradiation condition.     

A comparative study on the synthesis of 4‐alkyl‐1,3‐diarylpyrazoles using microwave irradiation and conventional thermal methods

A convenient synthesis of 4‐alkyl‐1,3‐diarylpyrazoles ( 2 ) under microwave irradiation as well as conventional thermal method using Vilsmeier cyclization is reported. Microwave irradiation has resulted in the reduction of time from hours to seconds.     

Solvent-free thermal and microwave-assisted [3 + 2] cycloadditions between stabilized azomethine ylides and nitrostyrenes. An experimental and theoretical study

The stereochemical outcomes observed in the thermal and microwave-assisted [3 + 2] cycloaddition between stabilized azomethine ylides and nitrostyrenes have been analyzed using experimental and computational approaches. It has been observed that, in the absence of solvent, three stereoisomers are formed, both under classical heating conditions and under microwave irradiation. This result contrasts with that observed in solution under classical thermal conditions. The 4-nitropyrrolidines obtained in this way can be aromatized under further microwave irradiation to yield mixtures of pyrroles and 4-nitropyrroles. It is found that ground state cycloadditions between imines and nitrostyrenes take place by three-step mechanisms. The first step involves enolization of the starting imine, and this is followed by a pseudopericyclic 10-electron [1.4]-hydrogen shift. Finally, the cycloaddition takes place by a relatively asynchronous aromatic six-electron supra-supra thermal mechanism.     

One-pot preparation of fluorinated propargylamines under microwave irradiation and solvent-free conditions

A facile one-pot method has been developed for the synthesis of fluorine-containing propargylamines by a three-component coupling of fluorinated aldehydes, amines, and alkynes, in the presence of copper (I) chloride under microwave irradiation and solvent-free condition. This process is an efficient alternative to traditional thermal reaction. All new compounds are fully characterized by spectral methods.     

Oxidative Aromatization of 1,3,5‐Trisubstituted 4,5‐Dihydro‐1H‐Pyrazoles Efficiently by Tetrabromine‐1,3,5,7‐Tetrazatricyclo[3.3.1.13,7]Decane Complex,Br4‐Tatcd,as a Novel Reagent both Under Microwave Irradiation and at Room Temperature

Oxidation of 1,3,5‐trisubstituted 4,5‐dihydro‐1H‐pyrazoles to the corresponding pyrazoles has been achieved by utilizing tetrabromine‐1,3,5,7‐tetrazatricyclo[3.3.1.1^3,7]decane complex, Br₄‐TATCD, in glacial acetic acid under microwave irradiation and conventional thermal condition at room temperature with excellent yields.     

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.     

微波促进催产素和赖氨加压素环肽的固相合成

以Rink Amide-MBHA树脂为载体, 采用Fmoc/tBu正交保护固相合成策略, 运用微波照射促进, 先快速高效地合成得到载有催产素或赖氨加压素还原型多肽的树脂, 再将连接在树脂上的各还原型多肽分别在微波促进条件下和常温条件下环合形成二硫键制得环肽, 最后用Reagent K试剂将环肽从树脂上裂解下来得到目标多肽的粗品. 利用HPLC法测定不同固相环合条件下得到的多肽粗品纯度, 结果显示经微波促进固相环合得到的多肽粗品纯度明显高于常温条件下得到的多肽粗品纯度. 粗品最后经过反相制备高效液相系统纯化并冻干得到目标多肽纯品, 通过电喷雾质谱法测定了制得的还原型多肽及相应环肽的分子量, 验证了它们的结构.     

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℃.     

微波辐射磷钨酸催化合成乙酸丁酯

以磷钨酸作催化剂 ,4A分子筛为脱水剂 ,采用微波辐射技术 ,用乙酸和丁醇直接合成乙酸丁酯 .考察了催化剂用量、微波辐射功率、时间、乙酸丁醇比对反应转化率的影响 .最佳反应条件为 :乙酸与磷钨酸的物质的量的比为 1∶0 .0 0 16 6 4,微波辐射功率及时间为 335W ,15min ,乙酸丁醇的物质的量的比为 1∶1.5 .此条件下转化率为 96 % .     

Synthesis of 6(5)-Methyl-5,7(4,6)-dinitro-1<Emphasis Type="Italic">H</Emphasis>-benzo[1.2.3]triazole under thermal conditions and under microwave irradiation

6(5)-Methyl-5,7(4,6)-dinitro-1H-benzo[1.2.3]triazole was synthesized by nitration of 6(5)-methyl-7(4)-nitro-1H-benzo[1.2.3]triazole under thermal conditions and under microwave irradiation. Advantages of the microwave irradiation mode are shown.     

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.     

利用微波技术合成4-芳基-5-甲氧羰基-6-甲基3,4-二氢吡啶-2-酮

微波辐射;二氢吡啶酮;芳醛;麦氏酸;利用微波技术合成4-芳基-5-甲氧羰基-6-甲基3;4-二氢吡啶-2-酮     

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.     

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.     

Esterification of dicarboxylic acids with benzyl alcohol under the action of the microwave radiation

Reaction of dicarboxylic acid with benzyl alcohol under the microwave irradiation proceeds faster as compared to the thermal conditions. The main reaction products are alkyl dicarboxylates, and the monoester and dibenzyl ether are formed as the side products. A proposal about the nature of the nonthermal effect in the reactions stimulated by the microwave irradiation is considered.     

Micowave assisted synthesis of benzo‐substituted macrocyclic diamides and their corresponding macrocyclic dithiodiamides

A synthesis of a series of macrocyclic diamides 3 in good yields by reacting the corresponding bis phenols 4 with the appropriate dihalo alkanes 6 either in solvent or in dry media under microwave irradiation. Thiation of 3 with P₂S₅ or Lawesson's reagent in solvent free conditions under microwave irradiation is also described.     

Microwave-assisted synthesis of new N4-[bi-（4-fluorophenyl）- methyl]-piperazine thiosemicarbazones under solvent-free conditions

Six new N4-[bi-（4-fluorophenyl）-methyl]-piperazine thiosemicarbazones 3a-f have been prepared starting from [bi-（4-fluorophenyl）-methyl]-piperazine in solvent-free condition under microwave irradiation with excellent yields. Their structures have been determined by elemental analysis, IR, MS and 1H NMR data.     

N－芳基－2－乙基－3－羟基－4－吡啶酮的微波合成

用微波辐射从2－乙基－3－羟基－4－吡喃酮和芳胺合成了系列N－芳基－2－ 乙基－3－羟基－4－吡啶酮，并对产物进行了紫外、红外、氢核磁和质谱表征。