An unusual synthesis of 3-(2-(arylamino)thiazol-4-yl)-2H-chromen-2-ones from ethyl 2-(chloromethyl)-2-hydroxy-2H-chromene-3-carboxylate via benzopyran ring opening

An unusual and unexpected synthesis of 3-(2-(arylamino)thiazol-4-yl)-2H-chromen-2-ones has been observed by the reaction of ethyl 2-(chloromethyl)-2-hydroxy-2H-chromene-3-carboxylate with various arylthioureas in ethanol under mild reaction conditions with excellent yields. The ambiguity in the structure of the obtained products has been solved by recording its single-crystal X-ray analysis. This protocol has been found to be a novel approach for the preparation of title compounds via benzopyran ring opening. A systematic plausible mechanism has been proposed for the formation of the product. Also, an efficient one-pot three-component method has been demonstrated for the formation of title compounds starting from salicylaldehyde.

     

Synthesis of benzopyrano[4,3-b](N-arylsulfonyl)indoles and benzopyrano[3,4-b](N-arylsulfonyl)indoles via intramolecular palladium-catalyzed aryl–aryl coupling reaction

A series of benzopyrano[3,4-b](N-arylsulfonyl) indole derivatives and benzopyrano[4,3-b](N-arylsulfonyl) indole derivatives were synthesized from 2- or 3-methylindole via intermolecular S( N )2 reaction and subsequent intramolecular palladium-catalyzed aryl-aryl coupling reaction for the first time. It was suggested that, besides using the Fischer cyclization, benzopyrano[4,3-b]indoles and benzopyrano[3,4-b]indoles could also be prepared via intermolecular S( N )2 reaction and sequential intramolecular palladium-catalyzed coupling reaction.     

Ultrasound assisted green synthesis of bis(indol-3-yl)methanes catalyzed by 1-hexenesulphonic acid sodium salt

1-Hexenesulphonic acid sodium salt as catalyst for green synthesis of bis(indol-3-yl)methanes was described. The reaction of indole with various aldehydes in water using ultrasound irradiation at ambient temperature for appropriate time using 1-hexenesulphonic acid sodium salt furnish the desired product in good to excellent yield. Utilization of aqueous medium, simple reaction conditions, isolation, and purification makes this manipulation very interesting from an economic and environmental perspective.     

Application of 2,4-bis(halomethyl)quinoline: synthesis and biological activities of 2,4-bis(benzofuran-2-yl)- and 2,4-bis(aroxymethyl)quinolines

Molecular Diversity - In the present investigation, the synthesis of a new type of halomethylquinoline building block, i.e., ethyl 4-(bromomethyl)-2-(chloromethyl)quinoline-3-carboxylate, and its...     

A general three-step one-pot synthesis of novel (<Emphasis Type="Italic">E</Emphasis>)-6-chloro-2-(aryl/hetarylvinyl)quinoline-3-carboxylic acids

In this work, a facile and general three-step one-pot synthesis of structurally new (E)-6-chloro-2-(aryl/hetarylvinyl)quinoline-3-carboxylic acid derivatives has been achieved from easily available ethyl 6-chloro-2-(chloromethyl) quinoline-3-carboxylate and aromatic or heteroaromatic aldehydes. This strategy features simple one-pot operation, tolerance of a wide range of substituents, and good yields. Moreover, these newly synthesized compounds belong to a new class of quinoline derivatives and could be good candidates for the development of more complex quinoline compounds for use in medicinal chemistry.     

CuCl催化苯腙和丙炔酸甲酯Michael加成反应的机理研究

本文采用密度泛函理论(DFT)中的M05方法针对性的研究了以CuCl为催化剂催化苯腙和丙炔酸甲酯发生Michael加成的微观反应机理.采用Gaussian09程序,使用6-31+G*(Cu采用赝势基组LanL2DZ)对化学反应过程中的反应物、中间体、过渡态分子的几何构型进行了优化,同时进行了频率计算,所有过渡态都有唯一虚频,中间体和过渡态分子结构的合理性得到了确认.通过自然键轨道(NBO)理论分析了分子轨道间的相互作用.通过理论计算发现CuCl催化苯腙和丙炔酸甲酯发生Michael加成反应的位点在苯腙的N原子上,反应的速控步骤活化能为34.86 kcal/mol,相关的理论研究结果与实验反应现象相吻合.     

Microwave-assisted one-pot multi-component reaction: synthesis of novel and highly functionalized 3-(pyranyl)- and 3-(dihydropyridinyl)indole derivatives

One-pot multi-component reaction of 3-cyanoacetyl indole, aromatic aldehydes and ethyl acetoacetate in the presence of \(\hbox {InCl}_{3}/\hbox {NH}_{4}\) OAc under microwave irradiation for 2–7 min afforded novel and highly functionalized 3-(pyranyl)- and 3-(dihydropyridinyl)indole derivatives, respectively, in good yield.     

H4SiW12O40/SiO2催化合成庚酸乙酯

以H4SiW12O40/SiO2为催化剂,庚酸和无水乙醇为原料,合成酒用香料庚酸乙酯。结果表明,复合硅钨杂多酸是合成庚酸乙酯的良好催化剂,适宜的工艺条件为：酸醇物质的量比为1∶2,催化剂用量3%,甲苯做带水剂8mL,反应时间2.5h,在此条件下产率可达49.5%。     

Reactivity of tetrahydrochromeno[2,3‐b]indoles: chromic indicators of cyanide

The synthesis and reactivity of a tetrahydrochromeno[2,3‐b]indoles are reported. Evidence for reversible ring‐opening is based on H/D exchange and trapping experiments. These compounds readily undergo reaction with tetra‐n‐butylammonium cyanide. The cyanide reaction is 10–100× faster when the solution is irradiated with 350 nm light. Reaction with trimethylsilyl cyanide occurs only with UV irradiation demonstrating photoreactivity. The rate of tetrahydrochromeno[2,3‐b]indole ring‐opening is greater for (i) Me substitution at the hemiaminal carbon (compared to Ph), and (ii) substitution of fluorine at the 9‐position of the indole. Under acidic conditions, the ring‐opened indolium ion is observed. Copyright © 2013 John Wiley & Sons, Ltd.     

Mechanistic study on Mo(CO)6‐catalyzed intramolecular [2 + 2] or [2 + 2 + 1] cycloaddition reaction of 5‐allenyl‐1‐ynes

By means of density functional theory, the Mo(CO)₆‐catalyzed intramolecular [2 + 2] or [2 + 2 + 1] cycloaddition reaction of 5‐allenyl‐1‐ynes was investigated. All the intermediates and transition states were optimized completely at B3LYP/6‐311++G(d,p) level (LANL2DZ(f) for Mo). Calculations indicate that the complexation of 5‐allenyl‐1‐ynes with Mo(CO)₆ occurred preferentially at the triple bond to give the complex M1 and then the complexation with the distal double bond of the allenes generates the complex M5 . In this reaction, Mo(CO)₆‐catalyzed intramolecular [2 + 2] cycloaddition is more favorable than [2 + 2 + 1] cycloaddition. The reaction pathway Mo(CO)₆ + R → M5 → T7 → M12 → M13 → T11 → M18 → P4 is the most favorable one, and the most dominant product predicted theoretically is P4 . The solvation effect is remarkable, and it decreases the reaction energy barriers. Copyright © 2011 John Wiley & Sons, Ltd.     

Green in water sonochemical synthesis of tetrazolopyrimidine derivatives by a novel core-shell magnetic nanostructure catalyst

A green approach for the one-pot four-component sonochemical synthesis of 5-methyl-7-aryl-4,7-dihydrotetrazolo[1,5-a]pyrimidine-6-carboxylic esters from the reaction of 2-cyano-guanidine, sodium azide, various aromatic aldehydes and methyl or ethyl acetoacetate in the presence of a catalytic amount of Fe₂O₃@SiO₂-(CH₂)₃NHC(O)(CH₂)₂PPh₂ as a new hybrid organic–inorganic core–shell nanomagnetic catalyst is described. This is the first design, preparation, characterization and application of the present nanomaterial and also the first ultrasound irradiated synthesis of the biologically and pharmaceutically important heterocyclic compounds in water as a green solvent. This novel sonocatalysis/nanocatalysis protocol offers several advantages such as high yields, short reaction times, environmentally-friendly reaction media, easily isolation of the products, simple preparation, full characterization and recoverability of the nanocatalyst by an external magnet and reusing several times without significant loss of activity.     

Synthesis of functionalized 5-imino-2,5-dihydro-furans through the reaction of isocyanides with activated acetylenes in the presence of ethyl bromopyruvate

Summary The reaction between alkyl(aryl) isocyanides and dibenzoylacetylene in the presence of ethyl bromopyruvate leads to ethyl 3,4-dibenzoyl-2-bromomethyl-5-alkyl(aryl)imino-2,5-dihydro-furan-2-carboxylates in high yields. Dialkyl acetylenedicarboxylates react with tert-butyl isocyanide and ethyl bromopyruvate to produce 3,4-dialkyl 2-ethyl 2-bromomethyl-5-tert-butylimino-2,5-dihydro-furan-2,3,4-tricarboxylates.     

Theoretical study of the mechanism of cycloaddition reaction between dichloromethylene silylene and formaldehyde

The mechanism of cycloaddition reaction between singlet dichloromethylene silylene and formaldehyde has been investigated using a MP2/6-31G* method, including geometry optimization and vibrational analysis for the stationary points on the potential energy surface. The energies of different conformations are calculated by CCSD(T)//MP2/6-31G* method. From the potential energy profile, it can be predicted that the cycloaddition reaction between singlet dichloromethylene silylene and formaldehyde has three competitive dominant reaction channels: (1) the two reactants first form a highly strained three-membered ring intermediate INT1c, which then isomerizes to an active four-membered ring product P1 via a transition state TS1c by ring-increasing reaction; Subsequently, P1 further reacts with formaldehyde to form the more stable silapolycyclic product P2; (2) the two reactants first form a four-membered ring intermediate INT1b by the [2?+?2] cycloaddition reaction, which then isomerizes to the four-membered ring product P3.1 via a transition state TS3.1, resulting from the chlorine transfer reaction; (3) INT1b further reacts with formaldehyde to form a silapolycyclic intermediate INT4, which then isomerizes to a silapolycyclic product P₄ via a transition state TS4.     

乙酸乙酯合成反应的实时在线拉曼光谱测量

本文报道一种用于在线拉光谱测量的技术。可以在工业生产过程中对产品的成分和工作条件进行实时的监测,在本实验中,用我们自己研制的光纤探头,配合现有的拉曼光谱装置对合成乙酸乙酯的化学反应过程进行了实时跟踪测量。得到了反应过程中乙醇-,乙酸和乙酸乙酯的拉曼光谱,从谱图分析了它们的特征峰与时间的关系,从而可由这些结果确定在此实验条件下反应物与生成物的浓度随时间的变化,进而可确定反应过程完成的时间。     

Total asymmetric synthesis of (–)-Phenylhistine, (–)-Aurantiamine and related compounds. Part I

A new general, short, and efficient strategy for the construction of dehydro-diketopiperazines was developed. Horner–Emmons type coupling between a phosphinyl glycine ester and a formyl heterocycle is the key coupling reaction, which proceeds in good-to-excellent yields on several sterically-hindered substrates. Moreover, racemization of the parent L-amino acids is avoided as a result of the mild basic conditions used. The selection of the NH protective group of the formyl heterocycle was crucial. N-tosylated heterocycles proved ideal for this reaction sequence. Thus, the title compounds, (–)-Phenylhistine and (–)-Aurantiamine, were prepared in high yield (four steps, 47% overall) and optical purity. Furthermore, the synthesis of unnatural derivatives including an indole analogue was successfully completed.     

Mass Spectrometry Study of 7-Chloro-3,4-dihydro-4,5-dioxo-3-substituted Aryl-2-thio-2H, 5H-pyrano [3,4-e]-1,3-Oxazine,their Morpholine and Alcohol Reaction Products

Retro Diels-Alder mechanism is the main fragmentation pattern of the 7-chloro Pyrano oxazine (2),7-morpholino pyrano oxasine (3),5-morpholino carbonyl-4-oxo-3-substituted phenyl-2-thio-1-3-oxazine-6-ylacetomorpholide (4) and ethyl-6-ethoxy carbonyl methyl-4-oxo-3-(substituted phenyl)-2-thio-2H-1,3-oxazine-5-carboxylate (5). Further fragmentation routes were also discussed.     

Hydrolysis and retro‐aldol cleavage of ethyl threo‐2‐(1‐adamantyl)‐3‐hydroxybutyrate: competing reactions

The hydrolysis of ethyl threo‐2‐(1‐adamantyl)‐3‐hydroxybutyrate ( 1 ) and the parent ester ethyl 3‐hydroxybutyrate ( 4 ) has been studied experimentally and computationally. In the hydrolysis of threo‐ester 1 with 2 M NaOH, predominantly retro‐aldol product was observed, whereas the hydrolyzed product was present in a minor amount. When the reaction is carried out under the same conditions with the parent ester ethyl 3‐hydroxybutyrate ( 4 ), hydrolyzed product is exclusively observed. The competitive pathways, namely hydrolysis and the retro‐aldol reaction for 1 and 4 were investigated using DFT calculations in the both gas and solvent phase. The calculated results in the solvent phase at B3LYP/6–31 + G* level revealed that the formation of retro‐aldol products is kinetically preferred over the hydrolysis of threo‐ester 1 in the presence of a base. However, the parent ester 4 showed that the retro‐aldol process is less favored than the hydrolysis process under similar conditions. The steric effect imposed by the bulky adamantyl group to enhance the activation barriers for the hydrolysis of the ethyl threo‐2‐(1‐adamantyl)‐3‐hydroxybutyrate ( 1 ) was further supported by the calculations performed with tert‐butyl group at the α‐carbon atom of ethyl 3‐hydroxybutyrate ( 7 ). Copyright © 2010 John Wiley & Sons, Ltd.     

New multicomponent approach for the synthesis of benzo[c]coumarin derivatives over MgO under solvent-free conditions

In this study, a three-component one-pot synthesis of select 5-amino-6-cyano-3-hydroxybenzo[c]coumarin compounds derived from salicylaldehydes, malononitrile, and ethyl acetoacetate is reported. The reaction is conducted on grinding over MgO at room temperature resulting in good yields.     

Simultaneous sonication assistance for the synthesis of tetrahydropyridines and its efficient catalyst ZrP2O7 nanoparticles

In this research, a general synthetic method for the synthesis of tetrahydropyridines were developed using ZrP₂O₇ nanoparticles under ultrasonic irradiations. Firstly by a simple and green process, nano zirconium pyrophosphate was prepared via sonication. Subsequently, this nanoparticle was used as an efficient catalyst for the synthesis of highly functionalized tetrahydropyridines via five-component reaction of aromatic aldehyde, amine and ethyl acetoacetate in ethanol under ultrasound irradiation. The present approach offers several advantages such as high yields, environmentally benign, simple work-up, excellent yield of products, short reaction times as well as recoverability and reusability of the catalyst.     

Copper(I)‐catalyzed reaction of unsymmetrical alkyne with HB(pin): a density functional theory study

With the aid of density functional theory calculations, we have investigated the mechanism of copper(I)‐catalyzed reaction between unsymmetrical alkyne 1‐phenyl‐1‐butyne and HB(pin). The results of the density functional theory calculations show that the reaction mechanism involves syn‐addition of catalyst ([NHC]CuH) (NHC = N‐heterocyclic carbene) to 1‐phenyl‐1‐butyne to form the alkenyl copper intermediates 2a and 5a , and then intermediates 2a and 5a react with HB(pin) to give intermediates 3 ( 3a , 3b ) and 6 ( 6a , 6b ), and finally elimination of catalyst completes the catalytic cycle and yields the α‐product P₁ and β‐product P₂ . We found that α‐product should be more favored than β‐product. The calculated results are consistent with the experimental findings. The present paper may provide a useful guide for understanding other analogous copper‐catalyzed hydroboration of unsymmetrical alkynes.