Synthese von para-substituierten phenyl-terpyridin liganden

Up to now the synthesis of para-substituted phenyl-terpyridine ligands was difficult with respect to the purification of the reaction products. We have found that these compounds can easily be isolated as hydrobromides from acetic acid. Starting from the hydrobromides the purification turned out to be easy. Synthesis of para-substituted Cl-, Br-, H₃C-, H₂BrC-, HO- 2,6-Bis(2-pyridyl)-4-phenylphyridine is reported.     

2-Aminoethanesulfonic acid: An efficient organocatalyst for green synthesis of spirooxindole dihydroquinazolinones and novel 1,2-(dihydroquinazolin-3(4H)isonicotinamides in water

Abstract

A facile and efficient one-pot procedure for the preparation of spirooxindole dihydroquinazolinone derivatives and new N-(4-oxo-2-phenyl-1,2-dihydroquinazolin-3(4H)-yl)isonicotinamides from reaction between isatoic anhydride, isoniazid and substituted aldehydes catalyzed by 2-aminoethanesulfonic acid (taurine) is describe. This new protocol has the advantages of environmental friendliness, good yields, and convenient operation. The reaction proceeds efficiently using water as green solvent and nontoxic catalysts that could be efficiently reused. Together with this simple workup procedure, use of the organocatalyst, and water as solvent without the need of column chromatographic purification, are the notable features of this methodology, which make this protocol a very efficient and green alternative to the traditional methods.     

Synthese von Fulvenen über 1-Chloralkyl-acetate

Synthesis of fulvenes via 1-chloroaklyl-acetates The synthesis of fulvenes (5) via l-chloroalkyl acetates (3) is extended to 6-alkyl-fulvenes with branched side-chains, to 6-phenylfulvene (5f) and 6-(2-furyl)fulvene (5g) , as well as to 6-vinylfulvenes ( 5h and 5i ) containing chlorine and acetoxy-substituents in ω-position. The reaction is carried out at low temperature under water-free conditions. The purification of the reaction products is simple. - An improved procedure for the preparation of pure fulvene ( 5a , R=R′=H) is reported.     

m-Iodosylbenzoic Acid: Recyclable Hypervalent Iodine Reagent for α-Tosyloxylation and α-Mesyloxylation of Ketones

m-Iodosylbenzoic acid–mediated reactions of various carbonyl compounds provided α-organosulfonyloxy carbonyl compounds in good yields. The final products could be easily isolated without any chromatographic purification by simple treatment of the crude mixture with an anionic exchange resin.     

Separation of 99Mo from a simulated fission product solution by precipitation with a-benzoinoxime

The formation property of Mo precipitate was investigated and improved the existing process was using H₂O₂ that acts as an interfering compound in a subsequent alumina adsorption process. The property of the Mo precipitate was investigated by using SEM, FTIR, TG-DTA, and XRD. The simulated solution consisted of 1M nitric acid containing seven elements (Mo, I, Ru, Zr, Ce, Nd, Sr) and their radioactive tracers. As a result, the precipitate was composed of the Mo precipitate and re-precipitated a-benzoinoxime which was added excessively for increasing the precipitation efficiency. It was confirmed that the Mo precipitate was formed by the reaction of two a-benzoinoxime molecules and one MoO₂ ²⁺. Molybdenum precipitate was dissolved in 0.4M NaOH solution within 5 minutes without H₂O₂. Hydrogen peroxide induced only the rapid dissolution of the a-benzoinoxime re-precipitate. Also, the dissolution method without H₂O₂ was favorable in the purification aspect because Zr and Ru were contained as a small fraction of 1.3% and 7.7%, respectively, in the dissolving solution.     

One-pot synthesis of novel (E)-3-(3,8a-dihydro-2H-oxazolo[3,2-a]pyridin-2-ylidene)chroman-2-one derivatives

An efficient synthetic procedure for the preparation of novel (E)-3-(3,8a-dihydro-2H-oxazolo[3,2-a]pyridin-2-ylidene)chroman-2-one derivatives was developed. A sequential one-pot, two-step tandem reaction starting from 3-(2-bromoacetyl)-2H-chromen-2-one derivatives synthesized, pyridine, and naphthols in the presence of triethylamine proceeded smoothly in acetonitrile under reflux conditions. In this process, 2-oxo-2H-chromen-3-yl)ethyl)pyridinium bromide derivatives as intermediate produced in situ, followed by Michael addition of naphthoxide anion and intramolecular cylization, resulted the corresponding products in good to high yields. All of the compounds were obtained in high purity without any use of more purification.     

Diastereoselektive synthese neuartiger Mannich-Basen mittels titanderivaten,vorläufige mitteilung

Diastereoselective Synthesis of Novel Mannich (Bases¹) through Titanium Reagents Trichlorotitanium dialkylamino-alkoxides ( 2 ; titanates of N, O-hemiacetals) are generated either from the corresponding lithium alkoxides and titanium tetrachloride (Scheme 1) or by addition of trichloro-dialkuylamino-titanium to aldehydes. The electrophilic (dialkylamino) alkylating reagents 2 are used to convert lithium enolates to β-dialkylamino-ketones and -esters 5 (Mannich bases), see Scheme 2 and Table. One diastereoisomer of the products 5g–5p thus obtained with cyclohexenolate is formed preferentially (66-84%). The configuration of the products of this first diastereoselective version of the Mannich reaction could not yet be determined. A typical procedure for carrying out the reaction is given.     

N‐heterocyclic carbene–palladium complexes for Suzuki–Miyaura coupling reaction with benzyl chloride and aromatic boronic acid leading to diarylmethanes

A family of N‐heterocyclic carbene–palladium(II)–N,N‐dimethylbenzylamine complexes ((NHC)LPdCl₂; L = N,N‐dimethylbenzylamine) were synthesized as well as characterized using single‐crystal X‐ray diffraction and spectroscopic data. These complexes exhibited higher catalytic activities for the Suzuki reaction of benzyl chlorides to afford diarylmethanes under milder conditions than other efficient (NHC)LPdCl₂ complexes. Using the optimum conditions, the expected coupling products were obtained in moderate to high yields. All reactions were carried out in air and all starting materials were used as supplied without purification.     

线型脲醛树脂的半结晶模板化作用

酸性条件下硅溶胶体系中尿素和甲醛聚合反应会产生脲醛树脂-氧化硅杂化沉淀. 沉淀的质量随有机组分比例的增加而增加, 当尿素和甲醛物质的量比≥1.0时生成沉淀的量为恒定最大值. 红外分析表明杂化材料在3348, 1635, 1572和784 cm^－1处产生了可被归结为线型结构(—[NHCONHCH₂]_n—)的特征吸收. XRD分析表明这种线型分子可形成氢键(C＝O…H—N)导向型的半结晶. 微分热重和XRD结果证明结晶物种在290 ℃完全分解. SEM表征显示半结晶杂化沉淀以三维网络结构为特征, 具有层状结晶的各向异性, 其初级粒子即使在室温下干燥也容易开裂. 随着反应时间的延长、酸性的增加或无机组分量的相对增加杂化粒子变得更加致密. 液氮吸附结果证明沉淀焙烧后所得氧化硅材料的结构具有层状孔结构性质, 其比表面积、孔尺寸和孔体积可以达到510 m²/g, 14.3 nm和1.68 cm³/g. 改变反应体系的酸性和反应组分配比等条件可以方便地控制杂化材料的结构.     

SiO2-NHC-CuI–Catalyzed N-Arylation of Imidazoles with Arylboronic Acids Under Base-Free Reaction Conditions

N-Arylation of imidazoles with arylboronic acids was efficiently carried out in the presence of a catalytic amount of SiO₂-NHC-Cu^I in methanol at room temperature under base-free reaction conditions. The reactions of a variety of arylboronic acids with imidazoles generated the corresponding products N-arylimidazoles in good to excellent yields. In addition, SiO₂-NHC-Cu^I could be recovered and recycled for six consecutive trials without significant loss of its reactivity.     

Synthesis of Both Enantiomers of Nine-Membered CF3-Substituted Heterocycles Using a Single Chiral Ligand: Palladium-Catalyzed Decarboxylative Ring Expansion with Kinetic Resolution

The two enantiomers of trifluoromethyl-benzo[c][1,5]oxazonines, (R)- 4 and (S)- 4 , can be selectively accessed with high enantiopurity by the Pd-catalyzed ring-expansion reaction of trifluoromethyl-benzo[d][1,3]oxazinones ( 1 ) with vinyl ethylene carbonates ( 3 ) using one antipode of a chiral ligand. Initially, the reaction proceeds by a double decarboxylative ring-expansion with kinetic resolution of 1 in the presence of a Pd-catalyst/chiral ligand to provide (R)- 4 with high enantiopurity. At the same time, the nonreactive antipode of 1 , (S)- 1 , which was recovered with an impeccable s factor of up to 713 and an ideal chemical yield, was transferred into the antipode of the products, (S)- 4 , with high enantiopurity by a second run of the Pd-catalyzed double decarboxylation reaction, but this time without any chiral auxiliary. Thus, both antipodes of the chiral trifluoromethyl heterocycles 4 can be obtained in excellent enantiopurity using only a single antipode of the chiral catalyst.     

Synthesis of multisubstituted N-(tosylamino)pyrrole derivatives by AuCl3-catalyzed cycloisomerization of the β-alkynyl hydrazones

A method for preparing multisubstituted N-(tosylamino)pyrrole derivatives through AuCl₃-catalyzed cycloisomerization of the β-alkynyl hydrazone compounds was described. The reaction could be carried out in one pot from the β-ketoesters to give the cyclized products in moderate to excellent yields with low catalyst loadings.     

Aqueous/organic biphasic hydroformylation of 1‐octene catalyzed by Co2(CO)8/Ph2P(CH2CH2O)nMe

The aqueous/organic biphasic hydroformylation of 1‐octene catalyzed by Co₂(CO)₈/Ph₂P(CH₂CH₂O)_nMe, an in situ formed thermoregulated phase‐transfer cobalt catalyst, has been developed. The catalyst activity in this biphasic system was as high as that in the homogeneous system. The yield of oxo‐products was 93% when the reaction was carried out at 180 °C and under 4.0 MPa syngas pressure for 20 h. The catalyst could be easily recovered in the aqueous phase by decanting after the reaction system was cooled, and reused in consecutive reaction without any treatment. The loss of Co in the organic phase was less than 1% on average of five successive runs. Copyright © 2012 John Wiley & Sons, Ltd.     

The Reaction of 1,2:3,4-Diepoxy-2,3-dimethylbutane with Nucleophiles

To find out whether the 1,4-addition to 1,2:3,4-diepoxides, which so far has been observed only once, is of a more general character, we investigated the reaction of a variety of O-, C-, N-, and S-nucleophiles with the model compound 1,2:3,4-diepoxy-2,3-dimethylbutane (Scheme 4). In several cases, 1,4-addition products could, indeed, be observed besides the expected 1,2-adducts (Table).     

Enantioselective Synthesis of Complex Fused Heterocycles through Chiral Phosphoric Acid Catalyzed Intramolecular Inverse-Electron-Demand Aza-Diels–Alder Reactions

A stable asymmetric intramolecular Povarov reaction has been established to provide an efficient method to access structurally diverse trans,trans-trisubstituted tetrahydrochromeno[4,3-b]quinolines in high stereoselectivities of up to >99:1 diastereomeric ratio and 99 % enantiomeric excess, without any purification step. Additionally, to facilitate large-scale application of this method, a low catalyst loading protocol was employed, 0.2 mol % chiral phosphoric acid, which provided the cycloadducts without any loss in yield and enantioselectivity. Theoretical studies revealed that the reaction occurred through a sequential Mannich reaction and an intramolecular Friedel–Crafts reaction, wherein the phosphoric acid acted as a bifunctional catalyst to activate the para-phenolic dienophile and N-2-hydroxy-2-azadiene simultaneously.     

An efficient one-pot synthesis of novel 6-hydroxy-14-aryl-8H-dibenzo[a,i]xanthene-8,13(14H)-diones derived from lawsone

An efficient and convenient procedure for the synthesis of novel 6-hydroxy-14-aryl-8H-dibenzo[a,i]xanthene-8,13(14H)-dione derivatives has been developed by one-pot, three-component condensation reaction between 2-hydroxynaphthalene-1,4-dione, aromatic aldehydes and 2,3-naphthalenediol in glacial acetic acid under reflux conditions. This domino reaction implies Knoevenagel condensation, Michael addition, intramolecular cyclization and dehydration. The reaction avoids tedious workup procedure due to the direct precipitation of products from the reaction medium. The notable features of this domino transformation are operational simplicity, clean reaction, easy handling, easy purification process and high yields of the products.

Graphical abstract

     

Synthesis of Difluoroglycine Derivatives from Amines,Difluorocarbene, and CO2: Computational Design,Scope, and Applications

A three-component reaction (3CR) for the synthesis of difluoroglycine derivatives has been achieved by using amines, difluorocarbene (generated in situ), and the abundant, inexpensive, and nontoxic C₁ source CO₂. Various tert-amines and pyridine, (iso)quinoline, imidazole, thiazole, and pyrazole derivatives were incorporated, and the corresponding products were isolated in solid form without purification by column chromatography on silica gel. Detailed reaction profiles of the 3CR were obtained from computational analysis using DFT calculations, and the results critically suggest that simple ammonia is not applicable to this reaction. In addition, as strongly supported by computational predictions, a new reagent that can generate difluorocarbene at 0 °C without any additives was discovered. Finally, radical substitution reactions of the obtained difluoroglycine derivatives under photoredox conditions, as well as a synthetic application as an N-heterocyclic carbene ligand are shown.     

Rapid Synthesis of 2‐Alkanol‐substituted Pyrrolo[2,3‐b]quinoxalines from Propargylic Alcohols via Copper‐free Sonogashira Coupling Reaction at Room Temperature

A practical and efficient procedure is established for the synthesis of 2‐alkanol‐substituted pyrrolo[2,3‐b]quinoxalines by the reaction of N‐alkyl‐3‐chloroquinoxaline‐2‐amines with propargylic alcohols. The reaction is carried out in the absence of any copper salt but in the presence of a catalytic amount of Pd(PPh₃)₂Cl₂ at room temperature. The Sonogashira coupling reaction step in this procedure is fast, producing clean products with high yields without contamination by unwanted homocoupling Glaser reaction products. The synthesized pyrroloquinoxaline derivatives are also screened against the three bacterial strains Micrococcus luteus, pseudomonas aeruginosa, and Bacillus subtilis.     

Facile and Stereospecific Synthesis of Various Dienones Using Task‐specific Ionic Liquid/Borohydride as Stable and Promoted Hydrogen Release Reagent

In this work, for the first time, task‐specific ionic liquid, 1‐n ‐butyl‐3‐methylimidazolium borohydride ([bmim]BH₄), was used as the medium as well as reagent for the regiospecific reduction of triarylpyrylium perchlorates to provide aromatic dienones as only product. The [bmim]BH₄ having a reactive anion also could promote the desired reaction thereby reducing the reaction times and improving the yields substantially. The products could be easily isolated from the reaction mixture by simple extraction.     

Highly diastereoselective synthesis of new heterolignan-like 6,7-methylendioxy-tetrahydroquinolines using the clove bud essential oil as raw material

The diastereoselective synthesis toward novel heterolignan-like 2-aryl-4-(4-hydroxy-3-methoxyphenyl)-6,7-methylendioxy-1,2,3,4-tetrahydroquinolines using for the first time clove bud essential oil as a renewable material was carried out. The synthetic protocol consisted of the hydrodistillation of dried flower buds, the solid base-catalyzed isomerization of the obtained essential oil enriched with eugenol in order to give isoeugenol and its participation, as a chemical reagent (dienophile) in the BF₃·OEt₂-catalyzed three component Povarov reaction, without previous purification. Final products were obtained as racemic mixtures of new trans-2,4-diaryl-r-3-Me-1,2,3,4-tetrahydroquinolines in moderate to good yields.