Efficient and Inexpensive Synthesis of Benzimidazoles and Quinoxalines

o-Phenylenediamines were reacted with carbonyl compounds, β-ketoesters, and 1,2-diketones in presence of ammonium salts to give benzimidazoles and quinoxalines in very good yields. Ammonium salts are commercial and environmentally benign catalysts.     

氧化铝和氧化锆催化剂上2-取代苯并咪唑和1,5-二取代苯并二氮的合成(英文)

In this study, alumina, zirconia, manganese oxide/alumina, and manganese oxide/zirconia have been investigated for their catalytic activity in the condensation reaction between o-phenylenediamine and an aldehyde or a ketone to synthesise 2-substituted benzimidazoles and 1,5-disubstituted benzodiazepines respectively. Surface area, surface acidity, and morphology of the catalysts have been analysed and correlated with their catalytic activity. The isolated yields of 2-substituted benzimidazoles and 1,5-disubstituted benzodiazepines are in the range of 30% to 95%. A good correlation between the amount of surface acid sites as well as the surface morphology of the catalysts and the catalytic activity has been observed. This method has been found to be simple and economical. The solid supports could be regenerated and reused without much loss in their activity. Further, the solid supports have been also found to be effective as general catalysts in the condensation of o-phenylenediamine with other substituted aldehydes and ketones.     

由邻苯二胺合成苯并咪唑、喹喔啉以及1-H-2,3－二氢1,5-苯并氮杂卓

A series of benzo-fused heteroaromatic compounds with 5-, 6- and 7-membered tings, such as benzimidazole,quinoxaline and 1H-1,5-benzodiazepine derivatives, were synthesized through condensation reaction of o-pheny1-enediamine with ary1 aldehydes or ketones. The experimental conditions were carefully examined, and the products were characterized by ^1H NMR, ^13C NMR, MS, IR and elemental analyses. In addition, the structure of a benzodiazaepine derivative with 7-membered ring was confirmed by single crystal X-ray diffraction analysis.     

The Synthesis of Benzimidazoles and Quinoxalines from Aromatic Diamines and Alcohols by Iridium‐Catalyzed Acceptorless Dehydrogenative Alkylation

Benzimidazoles and quinoxalines are important N‐heteroaromatics with many applications in pharmaceutical and chemical industry. Here, the synthesis of both classes of compounds starting from aromatic diamines and alcohols (benzimidazoles) or diols (quinoxalines) is reported. The reactions proceed through acceptorless dehydrogenative condensation steps. Water and two equivalents of hydrogen are liberated in the course of the reactions. An Ir complex stabilized by the tridentate P^N^P ligand N²,N⁶‐bis(di‐isopropylphosphino)pyridine‐2,6‐diamine revealed the highest catalytic activity for both reactions.     

Efficient Syntheses of 2-Substituted Benzimidazoles and Benzoxazoles from β-Keto Esters

An efficient synthetic method was developed to synthesize 2-substituted benzimidazoles and benzo- xazoles with β-keto esters as starting materials under mild reaction conditions, during which other functional groups are bearable from reactants to products.     

Saccharin as an Organocatalyst for Quinoxalines and Pyrido[2,3-b]pyrazines Syntheses

A room-temperature procedure using saccharin as catalyst has been described for the cyclocondensation of different 1,2-arylenediamines with various 1,2-dicarbonyl compounds, yielding either quinoxalines or pyrido[2,3-b]pyrazines. The reactions proceed in very short reaction times in methanol, and the target heterocycles are isolated in quantitative yields after addition of water, filtration, and drying. Substituted pyrido[2,3-b]pyrazines can also be reached regioselectively by reacting α-ketoaldehydes with 2,3-diaminopyridine.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

Syntheses and Chemistry of Very Robust Phosphiranes

BABAR-Phos is a very stable polycyclic phosphirane that readily forms complexes with rhodium and platinum. Depending on the oxidation state and further co-ligands, either phosphirane complexes or metallaphosphetanes (as products of a metal insertion) prevail. However, these insertion reactions are reversible. These rhodium BABAR-Phos complexes are active catalysts for the selective hydroboration of olefins.     

Microwave Flow Chemistry as a Methodology in Organic Syntheses,Enzymatic Reactions,and Nanoparticle Syntheses

Several studies have used microwaves as a heat source for carrying out various types of reactions employing circulation reaction vessels. The microwave flow chemical synthesis methodology is most appropriate in the use of microwaves in chemical syntheses. It can attenuate the problem of microwave heating (non‐uniform heating and penetration depth) and maximize the benefits (rapid heating and first temperature adjustments). In this brief review, we examine and explain some of the relevant features of microwave heating with applicative examples of the usage of microwave flow chemistry equipment in carrying out organic syntheses, enzymatic reactions, and (not least) nanoparticle syntheses.     

Novel Porphyrinoids for Chemistry and Medicine by Biomimetic Syntheses

In 1926 Hans Fischer and Bruno Walach synthesized the first porphyrins.

1 H. Fischer, B. Walach, Justus Liebigs Ann. Chem. 1926 , 450, 164–181.

Currently more than 1400 new articles concerning the synthesis and uses of porphyrins are published every year.

2 CAS Online search for 1994 .

However, the strong interest in these compounds indicated by this is in sharp contrast to their restricted availability. This is reflected in the current price of up to 500 DM for 5 mg of the most important porphyrins used in research and other applications (see Scheme 3). Biomimetic syntheses offer possibilities for an improved approach to porphyrins. By following the example set by nature it is also possible to obtain novel porphyrinoids which are different from naturally occurring porphyrins. This is exemplified by N,N′-bridged porphyrinogens, which have cage structures, inverted porphyrinoids (N atoms in the outer periphery) and, in particular, porphyrins with expanded systems. Among the family of expanded porphyrins are superarenes with up to 34 π electrons. Their pronounced aromaticity is indicated by ¹H NMR spectra, bond length equivalence, planar structures, and electrophilic substitution. With their strong absorption bands, the strongest of which have ? values of > 1000000, a value which exceeds the absorption intensity of all other organic pigments observed until now, and their ability to act as efficient photosensitizers, the expanded porphyrins open interesting perspectives in the fields of photochemistry and photomedicine.     

Facile Syntheses of the Three Major Metabolites of Thioridazine

Efficient, mild syntheses of the three major metabolites 2 – 4 of the important antipsychotic drug thioridazine ( 1 ) have been developed. The cardiotoxic metabolite 2 with a ring sulfoxide moiety was prepared in 96% yield by oxidation of 1 with NaIO₄ under acidic conditions. Four different procedures were elaborated for the selective side‐chain sulfide oxidation of 1 to mesoridazine ( 3 ), giving rise to yields of up to 91%. Finally, sulforidazine ( 4 ) was synthesised via oxidation of the sulfoxide 3 in the presence of either KMnO₄ or t‐BuOOH under basic conditions. Except for the oxidation with t‐BuOOH, all reactions took place under mild conditions within a few minutes, were nicely reproducible, and afforded medium‐to‐high yields of the desired products, which could be readily purified by column chromatography.     

苯并咪唑类化合物的合成研究进展

苯并咪唑类化合物应用广泛. 按不同的合成原料和合成方法进行分类, 综述了近年来苯并咪唑类化合物合成研究的新进展.     

绿色化学的范例——介绍Real-World Cases In Green Chemistry

“绿色”已成为 2 0世纪末并将继续成为 2 1世纪的一个重要词语 ,其含义不再仅仅是对一种颜色的表述。它具有更为广泛的社会、经济、生产和生活的内涵。“绿色食品” ,“绿色电池” ,“绿色化学” ,“绿色化学工业”跃然出现在各种报章杂志和广告宣传中 ,其中尤以“绿色化学”最为瞩目。“绿色化学”的口号最早产生于化学工业非常发达的美国。 1 990年 ,美国通过了一个“防止污染行动”的法令。 1 991年后 ,“绿色化学”由美国化学会 (ＡＣＳ)提出并成为美国环境保护局 (ＥＰＡ)的中心口号。 1 995年 ,美国总统克林顿设立了一个新奖项“总统…     

Relationships between the Chemistry of Dispersed Metals and Chemical Syntheses with Metal Atoms

An interesting and topical question in modern inorganic chemistry is: To what extent are the well-known chemistry of dispersed metals and the new technique of chemical synthesis with free metal atoms interrelated? Or in other words: Where, do these two facets of metal chemistry meet? In an attempt to glean an answer to this question three important aspects are considered: metal sols, activated metals as powders, and deposits in vacuum processes (evaporation and cathodic sputtering of metals).     

Syntheses and Crystal Structures of Three Novel Amino-acid-containing Polyoxomolybdosilicates

1 INTRODUCTION Polyoxometalates as metal-oxygen cluster ions have received a great deal of research due to their potential applications in catalysis, medicine and ma- terials science[1]. The modification of organic groups to the surface of polyoxoanions gives POMs more interesting character, and many derivatives of poly- oxoanions with organic ligands have been studied[2]. Particularly the potential applications of polyoxo- metalate as drugs in anti-viral and anti-AIDS have attracted t…     

化学创造教育目标、内容与形式探讨

如何在中学化学教学中开展创造教育,发展学生的创造力,这是化学教育面向现代化的重大课题。从目前中学化学教育状况来看,这一问题还未引起普遍的关注,长期以来,学生忙于应付作业,对付考试,使创造力发展受到了一定的阻碍。因此,注意结合中学化学教学实际,开展创造教育的研究与实践,培养学生创造性思维的认识技能,应是中学化学教育改革中值得重视的问题。本文拟就化学创造教育的目标、内容和形式做以探讨,以期引起化学界同仁的重视。     

Advances in the Synthesis of Ring-Fused Benzimidazoles and Imidazobenzimidazoles

This review article provides a perspective on the synthesis of alicyclic and heterocyclic ring-fused benzimidazoles, imidazo[4,5-f]benzimidazoles, and imidazo[5,4-f]benzimidazoles. These heterocycles have a plethora of biological activities with the iminoquinone and quinone derivatives displaying potent bioreductive antitumor activity. Synthesis is categorized according to the cyclization reaction and mechanisms are detailed. Nitrobenzene reduction, cyclization of aryl amidines, lactams and isothiocyanates are described. Protocols include condensation, cross-dehydrogenative coupling with transition metal catalysis, annulation onto benzimidazole, often using CuI-catalysis, and radical cyclization with homolytic aromatic substitution. Many oxidative transformations are under metal-free conditions, including using thermal, photochemical, and electrochemical methods. Syntheses of diazole analogues of mitomycin C derivatives are described. Traditional oxidations of o-(cycloamino)anilines using peroxides in acid via the t-amino effect remain popular.     

Recent Advances in the Synthesis of Isoquinoline-Fused Benzimidazoles

This review includes recent developments in the synthesis of benzo[4,5]imidazo[2,1-a]isoquinolines with particular attention given to categorizing protocols based on the structural features of the ring architecture and crystallographically characterized reaction products.     

Microwave-Assisted Synthesis of Quinoxalines in PEG-400

A rapid and efficient procedure for the synthesis of quinoxaline derivatives has been achieved by condensation of aryl-1,2-diamines with 1,2-dicarbonyl compounds catalyzed by polyethylene glycol under CEM-focused microwave-irradiation conditions.