VO(acac)_2 catalyzed condensation of o-phenylenediamine with aromatic carboxylic acids/aldehydes under microwave radiation affording benzimidazoles

Vanadyl acetylacetonate,VO（acac）₂,has been found to be very effective catalyst for synthesis of a variety of benzimidazoles under solvent-free condition.The methodology involves the exposure of a mixture of o-phenylenediamine and a selected aromatic carboxylic acid/aldehyde to microwave radiation without the use of any solvent or supporting agents.The benzimidazoles were obtained in quick time with high yields.     

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.     

Solvent-free Synthesis of 5-Azacytosine with Microwave Activation

5-Azacytosine (4-amino-1,2-dihydro-1,3,5-triazin-2-one) is a very important intermediate in the synthesis of 5-azacytidine which showed remarkable bacteriostatic and cytostatic activity as well as against T-4 lymphoma and L-1210 leukemia in mice. Starting with N-cyanoguanidine (dicyandiamide) and formic acid, under the solvent-free microwave activation,we synthesized 5-azacytosine in short time (4min) with good yield (60.4%). The structure of the product was confirmed by 1HNMR and Elemental analysis.In this paper, a new and rapid synthesis of 5-azacytosine has been reported for the first time in microwave oven. N-cyanoguanidine (0.05tmol) and anhydride formic acid (0.18mol) were stirred well. Then irradiate the reaction mixture in microwave oven for the specified time (4min) under solvent-free condition. After the reaction was complete, the resulting solid was disperated in warm absolute ethanol (10ml), cooled to 0℃, filtered and dried in vacuum to yield the crude product. The pure product was obtained by recrystallization.     

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.     

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.     

Environment friendly protocol for the synthesis of nitriles from aldehydes

<正>A rapid and eco-friendly one-pot protocol for the synthesis of nitriles has been developed by treating various araldehydes bearing electron withdrawing as well as electron donating groups with hydroxylamine hydrochloride in the presence of non-toxic,non-corrosive and reusable zinc oxide(ZnO) as the catalyst under solvent-free microwave irradiation.The present approach offers the advantages of a clean reaction,simple methodology,employing readily available catalyst,short reaction duration(1 min),high selectivity;and high yield(90-98%).     

超声辐射下的无溶剂Knoevenagel缩合反应

在无溶剂,无催化剂,超声辐射下芳香醛与丙二腈发生knoevenagel缩合反应,合成了一系列苄叉基化合物,通过熔点的测定,红外光谱、核磁共振及元素分析对产物的结构进行了表征。结果表明,该方法不但化学选择性好,而且产物易处理,对环境污染小,符合绿色化学的要求。     

Solvent-free aldol condensations: synthesis of ferrocenyldienones

The aldol condensation of ferrocenecarbaldehyde and acetylferrocene with aldehydes and ketones proceeded more efficiently and stereoselectively in the absence of a solvent than in solution. In all the cases, E-configured enones were obtained, which was confirmed by X-ray crystallographic studies of one of the products.     

Solvent-free synthesis of 2-amino-4-arylthiazoles under microwave irradiation

2-Amino-4-arylthiazoles were prepared in a one-pot solvent-free procedure by reaction of p-substituted acetophenones with thiourea and iodine under microwave irradiation.     

Solvent-free alkylation of dimethyl malonate using benzyl alcohols catalyzed by FeCl_3/SiO_2

Activated methylene compound such as dimethyl malonate reacted readily with benzylic alcohols in the presence of ferric chloride/silica gel mixture(FeCl_3/SiO_2) under microwave irradiation to produce benzylic derivative of dimethyl malonate in high yields in solvent-free condition.     

Clean and fast oxidative transformation of thiols to disulfides under solvent-free conditions

We present here a fast, solvent-free synthesis of symmetrical disulfides using solid supported catalyst (Al₂O₃/KF). The reaction was performed at room temperature, by gentle heating or under MW irradiation. This efficient and improved method is general for liquid thiols, affording the disulfides in good to excellent yields. The catalytic system can be re-used two times without previous treatment and with comparable activity.     

Solvent-free conjugated addition of thiols to citral using KF/alumina: preparation of 3-thioorganylcitronellals, potential antimicrobial agents

A general, clean and easy method for the conjugated addition of thiols to citral promoted by KF/Al₂O₃ under solvent-free conditions at room temperature or under MW irradiation is described. It was found that the same protocol is applicable to the direct reaction of thiophenol with essential oil of lemon grass (Cymbopogon citratus) to afford directly 3-thiophenylcitronellal, a potential bactericide agent. The method was extended to others electron-poor alkenes with excellent results. The catalytic system can be reused up to three times without previous treatment with comparable activity.     

Solvent-free synthesis of novel unsymmetric chenodeoxycholic acid bis thiocarbazone derivatives promoted by microwave irradiation and evaluation of their antibacterial activity

Eleven new non-symmetric chenodeoxycholic acid bis thiocarbazones were efficiently synthesized via the condensation of steroidal diketones (methyl (5β)-3,7-dioxocholan-24-oate) and substituted benzaldehyde thiocarbohydrazones by means of microwave irradiation. Compared with the conventional heating method, the yields were increased from 31–58% to 80–89% and the reaction times were reduced from 420–520 min to 5.0–7.5 min. The structures of these novel compounds were characterized by spectral data and elemental analysis. Four compounds (7a, 7c, 7f and 7g) possess excellent activity against Bacillus subtilis and Staphylococcus aureus.     

对甲酰基苯氧基甲基型聚苯乙烯树脂的简便快速制备

以Merrifield树脂为原料,家用微波炉为反应装置,在微波照射的相转移催化(MI-PTC)条件下,简便快速地合成了3种甲酰基功能化的交联聚苯乙烯树脂——对甲酰基苯氧基甲基树脂、对甲酰基-2-甲氧基苯氧基甲基树脂和对甲酰基-3-甲氧基苯氧基甲基树脂.在MI-PTC条件下,树脂制备过程所需的时间不超过1h,而传统加热制备方法则需要8h以上.实验中,微波输入功率为158W,反应过程用FTIR谱进行监测,碘化四丁基铵被考察为最好的相转移催化剂.该方法提供了一种反应条件温和、简便快速地制备功能化树脂的途径.     

Solvent-free reduction of aldehydes and ketones using solid acid-activated sodium borohydride

A simple and convenient procedure for the reduction of aldehydes and ketones with sodium borohydride activated by solid acids such as boric acid, benzoic acid, and p-toluenesulfonic acid monohydrate under solvent-free conditions is described.     

微波相转移催化合成DL—苯丙氨酸

在微波作用下,仅用1min便完成了苯甲醛亚胺的固—液相转移催化苄基化反应,然后经酸水解得到d1—苯丙氨酸,全程总产率为62.5×10(-2)。     

Solvent-free Efficient Synthesis of Symmetrical Isocyanurates by a Combination Catalyst: Sodium Saccharin and Tetrabutylammonium Iodide

Summary. Combination of sodium saccharin and tetrabutylammonium iodide as a novel anionic catalyst system promotes selectively the trimerization of isocyanates to give symmetrical isocyanurates under solvent-free conditions.Present Address: College of Chemistry, Isfahan University of Technology, Isfahan, 84154, Iran     

Solvent-free Ugi four-component condensation: application to synthesis of philanthotoxins-12 analogues

Philanthotoxins-12 analogues was synthesized by a highly convergent approach, utilizing an efficient, simple, and convenient one-pot Ugi four-component solvent-free method as key step, followed by removal of the protecting groups in the presence of trifluoroacetic acid.     

Synthesis of (Z)-3-Butylidene-4-hydroxyphthalide

(Z)-3-Butylidene-4-hydroxyphthalide (5) was first synthesized regio- and stereoselectively from 3-methoxybenzyl alcohol (1)     

Regiospecific Synthesis of Dioxabicyclooctanes Containing a Terminal Prenyl Sidechain

A Wittig reaction employing the ylide generated from isopropyl triphenylphosphonium bromide with THP-protected aldol intermediate 8 constitutes the key step in a regiospecific synthesis of olefin 1 in the total synthesis of zoapatanol analogue 2a.