Base-Mediated Biginelli-Like Reaction Ignited by Aromatic Isocyanate: A Facile One-Pot Synthesis of N 4-Aryl-5-carboxyl-6-methyl Cytimidine Derivatives

The new three-component Biginelli reaction of aromatic isocyanate, ethyl acetoacetate, and substituted urea (or thiourea as well as guanidine) is described for the first time. In this reaction, N ⁴-aryl-5-carboxyl-6-methyl cytimidine derivatives were obtained in moderate to excellent yields by employing DBU as a highly effective catalyst. This methodology provides several advantages such as good functional group tolerance, excellent yields, atom efficiency, and experimental simplicity.     

One-pot facile synthesis of polysubstituted pyridines via tandem reaction of the Blaise reaction intermediates and 3-formylchromones

A novel tandem one-pot method for the synthesis of polysubstituted pyridine derivatives has been developed via Knoevenagel-type reaction and subsequent 6π electrocyclization of the Blaise reaction intermediates and 3-formylchromones. Short reaction time, moderate to good yields and excellent functional group tolerance have been accomplished in this protocol.     

纤维素在亚/超临界甲醇中液化条件对主要化合物产物的影响

在反应温度240-320 ℃、甲醇用量0-200 mL、反应时间0-200 min的条件下,采用间歇式高温高压反应釜对玉米秸秆纤维素在亚/超临界甲醇中进行液化实验,结合GC-MS分析,研究不同液化反应条件下,生物油中轻油、重油产率及液化产物中烃类、醇类、酯类、酸类等主要化合物的组分分布及其变化规律。结果表明,反应温度和甲醇用量对化合物的分布与含量影响较大,反应温度和甲醇用量增加,促进纤维素向烃类、醇类、酯类转化,各化合物含量随之增加,并使轻油、重油产率升高,当反应条件为：甲醇用量160 mL,温度320 ℃,反应时间30 min时,生物油产率达到最高25.1%。生物油中组分含量顺序为：烃类>醇类>酯类>酸类,各化合物最高相对含量分别为77.2%、19.0%、30.9%、20.8%。初步分析发现,随着温度的升高和甲醇量的增加,自由基活性逐渐增强,当甲醇用量超过160 mL、温度超过300 ℃时,醇类以及酯类等化合物进一步发生氧化、缩合等反应形成酸类等化合物,造成化合物产率减小,进而使生物油产率降低。     

Poly(ethyleneglycol) (PEG): a rapid and recyclable reaction medium for the DABCO-catalyzed Baylis-Hillman reaction

PEG (400) has been used as a rapid and recyclable reaction medium for the Baylis-Hillman reaction with the conventional basic catalyst DABCO (20 mol %) with very good yields of products. Recyclability is achieved with no further addition of DABCO to the reaction medium for over four runs without substantial loss in yields. Incidentally, DABCO is recycled for the first time in this transformation.     

Three-Component Reaction of β-Ketosulfone,Formaldehyde, and Thiol or Thiophenol in Water

Abstract

A three-component reaction of β-ketosulfone, formaldehyde, and thiol or thiophenol was developed. The reaction was performed in pure water under a catalyst-free condition, and the corresponding Mannich-type thioethers were obtained in good to excellent yields. Finally, a one-pot stepwise four-component reaction of sodium benzenesulfinate, α-bromoketone, β-ketosulfone, and thiophenol was also developed.     

Silica triflate as an efficient reagent for the solvent-free synthesis of coumarins

Silica triflate,as a new silica-based reagent,can be used for the efficient synthesis of 4-substituted coumarins via a Pechmann reaction under solvent-free reaction conditions.All reactions were performed at 80℃in good to high yields.     

Effect of microwave irradiation on the reactivity of chloroarenes in Suzuki—Miyaura reaction

Simple catalytic systems for the Suzuki—Miyaura reaction of aryl chlorides under microwave conditions were tested. Microwave irradiation facilitated the reaction course. The catalyst, base, and solvent effect were studied and two reaction systems offered reasonable to high yields within a short time.     

Domino synthesis of fused hexacyclic imidazoquinolinoacridinones catalyzed by CuI/l-proline

A three-component reaction of 2-halogenated aromatic aldehydes, 1H-benzo[d]imidazol-5-amine and cyclohexane-1,3-diones is described, and gives imidazoquinolinoacridinone derivatives in good yields catalyzed by CuI/l-proline. This Domino reaction constructs a fused hexacyclic skeleton in one-pot containing two new rings, six new bonds and an Ullmann-type C–N bond coupling reaction.     

脯氨酰肼小分子催化的环己酮的直接α-硫代反应

研究了脯氨酰肼有机小分子催化环己酮的直接α-硫代反应. 考察了3种不同硫代试剂、9种溶剂、6种脯氨酰肼催化剂等对反应的活性和收率的影响. 结果表明, 硫代试剂、溶剂及催化剂的结构对反应的活性和反应收率均有较大的影响. 在优化条件下, 即以邻苯二甲酰亚胺为硫代试剂, 甲苯为溶剂, 脯氨酰肼1和4催化的环己酮的硫代反应活性比较高, 室温反应12 h, 收率达98%. 脯氨酰肼催化该类反应条件温和, 操作简单, 在药物合成中具有一定的应用潜力.     

Amino-β-lactams in Ugi reaction: An efficient method for preparation of functionalized peptidomimetics

A synthetic strategy for the Ugi reaction on amino-β-lactam synthon 1 was developed. The Ugi reaction products 5 were obtained in satisfactory yields (47–78%) and generally, low diastereoselectivity (up to 72:28 dr). In case of Ugi products 5 derived from cyclohexylcarbaldehyde and amino-β-lactam 1, the reaction yields were lower (38–61%) but the products were obtained in high diastereoselectivity (>95:5).     

Regioselective synthesis of 2,3-disubstituted 1-alkyl pyrrolo[2,3-b] quinoxalines through palladium-catalyzed Heck reaction of chalcones and evaluation of their anti-bacterial activities

The regioselective synthesis of 1-alkyl-2-aryl-3-acyl pyrrolo[2,3-b]quinoxalines through palladium-catalyzed Heck coupling reaction/heteroannulation was reported. The reaction of N-alkyl/benzyl-3-chloroquinoxaline-2-amines with chalcones catalyzed by Pd(OAc)₂ in the presence of KO^tBu, as the base, in DMSO afforded the desired products in good-to-high yields. The MIC and MBC determinations revealed that these compounds could be used in the future research works for the development of antibiotics.     

An easy and general protocol for multicomponent coupling reactions of aldehydes, amides, and dienophiles

An improved procedure for the three-component coupling reaction of aldehydes, amides, and dienophiles (AAD-reaction) has been developed. The use of microwave technology enables the endo-selective synthesis of N-acyl cyclohexenylamines via condensation of readily available aldehydes and amides, and subsequent Diels-Alder reaction with electron-deficient dienophiles in significantly improved yields. Advantageously, there is no need of employing additional solvents and reaction times are drastically reduced compared to similar thermal reactions.     

A green one-pot three-component synthesis of α-aminophosphonates under solvent-free conditions and ultrasonic irradiation using Fe3O4@SiO2-imid-PMAn as magnetic catalyst

An efficient and environment friendly process for the synthesis of α-aminophosphonates has been devised. Through a one-pot three-component condensation of various aldehydes, amines, and triethyl phosphite in the presence of Fe₃O₄@SiO₂-imid-PMAⁿ nanoparticles as magnetic catalysts under solvent-free conditions and ultrasonic irradiation, α-aminophosphonates were obtained with excellent yields. The reactions under solvent-free conditions at room temperature are compared with the ultrasonic-assisted reactions. This new procedure has notable advantages such as short reaction time, excellent yields, easy purification, and the absence of any tedious workup or purification. The aforementioned catalyst could be easily recovered by an external magnetic field and can be reused for six consecutive reaction cycles without significant loss of activity. In addition, SEM and DLS of the catalyst after the reaction cycle were investigated.     

Novel and efficient synthesis of triazolobenzodiazepine analogues through the sequential Ugi 4CR-click-N-arylation reactions

An efficient approach for the synthesis of N-alkyl-2-aryl-2-(6-oxo-4H-benzo[f][1,2,3]triazolo[1,5-a][1,4]diazepin-5(6H)-yl)acetamides is described. The protocol involves Ugi four-component reaction of 2-bromobenzoic acid, propargylamine, aldehydes and isocyanides followed by in situ sequential click reaction of azide ion with triple bond and N-arylation reaction to afford desired products in good to excellent yields.     

Microwave promoted diastereoselective synthesis of dihydroindeno[1,2-b]furans via one-pot three-component reaction in solvent-free conditions

An efficient method was developed for the synthesis of fused dihydroindeno[1,2-b]furans. One-pot three-component reaction of 1,3-indanedione, aromatic aldehyde and pyridinium ylide in the presence of triethylamine under microwave-irradiation in solvent-free conditions afforded dihydroindeno[1,2-b]furans in a diastereoselective manner in excellent yields.     

Efficient synthesis of diarylidene octahydroacridines by one-pot multi-component tandem reactions

A one-pot multi-component reaction is developed for the efficient synthesis of 4,5-dibenzylidene octahydroacridines in high yields. The reaction is performed by the tandem reaction of three molar equivalent aromatic aldehydes with two molar equivalent 4-alkylcyclohexanone in the system of NH₄OAc/HOAc under microwave irradiation.      

TFA-mediated intramolecular Friedel-Crafts reaction. An efficient metal and halogen free route to stereoselective synthesis of benzocycles

6-Acetoxy-4-alkenyl arenes undergo regio- and stereoselective intramolecular Friedel-Crafts reaction affording benzocycles in moderate to excellent yields in TFA/HOAc (3:1). It was observed that introduction of alkyls or phenyl group to the allylic acetate moiety facilitates the cyclization reaction. The optically active tricyclic (4bR,8aS)-4b,7,8,8a,9,10-hexahydrophenanthrene skeleton could also be easily obtained in excellent yields.     

Synthesis of substituted biaryls via Suzuki,Stille and Hiyama cross‐coupling and homo‐coupling reactions by CN‐dimeric and monomeric ortho‐palladated catalysts

The catalytic activity of dimeric [Pd{C₆H₂(CH₂CH₂NH₂)–(OMe)₂,2,3}(μ‐Br)]₂ and monomeric [Pd{C₆H₂(CH₂CH₂NH₂)–(OMe)₂,2,3}Br(PPh₃)] complexes as efficient, stable and air‐ and moisture‐tolerant catalysts was investigated in the Suzuki, Stille and Hiyama cross‐coupling and homo‐coupling reactions of various aryl halides. Substituted biaryls were produced in excellent yields in short reaction times using catalytic amounts of these complexes. The monomeric complex was demonstrated to be more active than the corresponding dimeric catalyst for the cross‐coupling reaction of unreactive aryl bromides and chlorides. The combination of homogeneous metal catalysts and microwave irradiation gave higher yields of products in shorter reaction times. Copyright © 2013 John Wiley & Sons, Ltd.     

A rapid and convenient synthesis of 5-unsubstituted 3,4-dihydropyrimidin-2-ones and thiones

A rapid and convenient synthesis of 5-unsubstituted 3,4-dihydropyrimidin-2-ones and thiones was developed. The reaction involves a one-pot reaction between oxalacetic acid, thiourea/urea, and aldehyde under microwave irradiation and provides the products in good yields and much shorter reaction times.     

Synthesis of linear monodisperse vinylene-linked phenothiazine oligomers

A series of linear monodisperse vinylene-linked phenothiazine oligomers have been synthesized by alternate Heck reaction and Wittig reaction in good yields. It was found that their absorption and fluorescence emission bands red-shifted with increasing phenothiazine units due to extending of the conjugated degree. The fluorescent quantum yield increased from OPTZ1 to OPTZ6, and the Φ_F of OPTZ6 was close to phenothiazine-based polymers.