Multicomponent reactions of amines with aldehydes and H<Subscript>2</Subscript>S as efficient route to heterocycles and thioaza macrocycles

Here we provide new experimental results on multicomponent reactions of amines with aldehydes and H₂S in the directed synthesis of functionally-substituted 1,3-thiazetidines, 1,3,5-dithiazinanes, 1,3,5-thiadiazinanes, 1,5-dithia-3,7-diazacyclooctanes, and thioaza macrocycles. X-ray analysis gave insight into the structure of the synthesized compounds. New kinds of multicomponent reactions (MCR) have been discovered and characterized.     

Synthesis of $$\upalpha $$-amino-1,3-dicarbonyl compounds via Ugi flow chemistry reaction: access to functionalized 1,2,3-triazoles

The Ugi multicomponent reaction has been used as an important synthetic route to obtain compounds with potential biological activity. We present the rapid and efficient synthesis of \(\upalpha \)-amino-1,3-dicarbonyl compounds in moderate to good yields via Ugi flow chemistry reactions performed with a continuous flow reactor. Such \(\upalpha \)-amino-1,3-dicarbonyl compounds can act as precursors for the production of \(\upalpha \)-amino acids via hydrolysis of the ethyl ester group as well as building blocks for the synthesis of novel compounds with the 1,2,3-triazole ring. The \(\upalpha \)-amino acid derivatives of the Ugi flow chemistry reaction products were then used for dipeptide synthesis.     

Lipase-catalyzed polyester synthesis – A green polymer chemistry

This article is a short comprehensive review describing in vitro polyester synthesis catalyzed by a hydrolysis enzyme of lipase, most of which has been developed for these two decades. Polyesters are prepared by repeated ester bond-formation reactions; they include two major modes, ring-opening polymerization (ROP) of cyclic monomers such as cyclic esters (lactones) and condensation polymerization via the reaction between a carboxylic acid or its ester group and an alcohol group. Polyester synthesis is, therefore, a reaction in reverse way of in vivo lipase catalysis of ester bond-cleavage with hydrolysis. The lipase-catalyzed polymerizations show very high chemo-, regio-, and enantio-selectivities and involve various advantageous characteristics. Lipase is robust and compatible with other chemical catalysts, which allows novel chemo-enzymatic processes. New syntheses of a variety of functional polyesters and a plausible reaction mechanism of lipase catalysis are mentioned. The polymerization characteristics are of green nature currently demanded for sustainable society, and hence, desirable for conducting ‘green polymer chemistry’.     

High pressure: A promising tool for multicomponent reactions

In this paper the application of high pressure in multicomponent reactions is discussed. Using high pressure the scope of certain multicomponent reactions can be increased. Reactions are described that can only be performed in a multicomponent fashion when high pressure catalysis is applied. An overview of high pressure catalysed multicomponent reactions is presented with special attention to the domino [4 + 2]/[3 + 2] cycloaddition reaction.     

Formamide and the origin of life

The complexity of life boils down to the definition: “self-sustained chemical system capable of undergoing Darwinian evolution” (Joyce, 1994) [1]. The term “self-sustained” implies a set of chemical reactions capable of harnessing energy from the environment, using it to carry out programmed anabolic and catabolic functions. We briefly present our opinion on the general validity of this definition.Running anabolic and catabolic functions entails complex chemical information whose stability, reproducibility and evolution constitute the core of what is dubbed genetics.Life as-we-know-it is made of the intimate interaction of metabolism and genetics, both built around the chemistry of the most common elements of the Universe (hydrogen, oxygen, nitrogen, carbon). Other elements like phosphorus and sulphur play important but ancillary and potentially replaceable roles.The reproducible interaction of metabolic and genetic cycles results in the hypercycles of organization and de-organization of chemical information that we consider living entities. In order to approach the problem of the origin of life it is therefore reasonable to start from the assumption that both metabolism and genetics had a common origin, shared a common chemical frame, were embedded in physical–chemical conditions favourable for the onset of both.The most abundant three-atoms organic compound in interstellar environment is hydrogen cyanide HCN, the most abundant three-atoms inorganic compound is water H₂O. The combination of the two results in the formation of formamide H₂NCOH. We have explored the chemistry of formamide in conditions compatible with the synthesis and the stability of compounds of potential pre-genetic and pre-metabolic interest. We discuss evidence showing (i) that all the compounds necessary for the build-up of nucleic acids are easily obtained abiotically, (ii) that essentially all the steps leading to the spontaneous generation of RNA are abiotically possible, (iii) that the key compounds of extant metabolic cycles are obtained in the same chemical frame, often in the same test tube.How close are these observations to a plausible scenario for the origin of life?     

Tunable Aminooxy‐Functionalized Monolayer‐Protected Gold Clusters for Nonpolar and Aqueous Oximation Reactions

Aminooxy (–ONH₂) groups are well known for their chemoselective reactions with carbonyl compounds, specifically aldehydes and ketones. The versatility of aminooxy chemistry has proven to be an attractive feature that continues to stimulate new applications. This work describes application of aminooxy click chemistry on the surface of gold nanoparticles. A trifunctional amine‐containing aminooxy alkane thiol ligand for use in the functionalization of gold monolayer‐protected clusters (Au MPCs) is presented. Diethanolamine is readily transformed into an organic‐soluble aminooxy thiol ( AOT ) ligand using a short synthetic path. The synthesized AOT ligand is coated on ≤2‐nm‐diameter hexanethiolate‐(C₆S)‐capped Au MPCs using a ligand‐exchange protocol to afford organic‐soluble AOT /C₆S (1:1 ratio) Au mixed monolayer‐protected clusters (MMPCs). The synthesis of these Au(C₆S)( AOT ) MMPCs and representative oximation reactions with various types of aldehyde‐containing molecules is described, highlighting the ease and versatility of the chemistry and how amine protonation can be used to switch solubility characteristics.     

Chiral poly-rare earth metal complexes in asymmetric catalysis

Asymmetric catalysis is a powerful component of modern synthetic organic chemistry. To further broaden the scope and utility of asymmetric catalysis, new basic concepts for the design of asymmetric catalysts are crucial. Because most chemical reactions involve bond-formation between two substrates or moieties, high enantioselectivity and catalyst activity should be realized if an asymmetric catalyst can activate two reacting substrates simultaneously at defined positions. Thus, we proposed the concept of bifunctional asymmetric catalysis, which led us to the design of new asymmetric catalysts containing two functionalities (e.g. a Lewis acid and a Brønsted base or a Lewis acid and a Lewis base). These catalysts demonstrated broad reaction applicability with excellent substrate generality. Using our catalytic asymmetric reactions as keys steps, efficient total syntheses of pharmaceuticals and their biologically active lead natural products were achieved.     

Catalytic degradation of organic dyes using biosynthesized silver nanoparticles

The green synthesis of metallic nanoparticles paved the way to improve and protect the environment by decreasing the use of toxic chemicals and eliminating biological risks in biomedical applications. Plant mediated synthesis of metal nanoparticles is gaining more importance owing to its simplicity, rapid rate of synthesis of nanoparticles and eco-friendliness. The present article reports an environmentally benign and unexploited method for the synthesis of silver nanocatalysts using Trigonella foenum-graecum seeds, which is a potential source of phytochemicals. The UV–visible absorption spectra of the silver samples exhibited distinct band centered around 400–440 nm. The major phytochemicals present in the seed extract responsible for the formation of silver nanocatalysts are identified using FTIR spectroscopy. The report emphasizes the effect of the size of silver nanoparticles on the degradation rate of hazardous dyes, methyl orange, methylene blue and eosin Y by NaBH₄. The efficiency of silver nanoparticles as a promising candidate for the catalysis of organic dyes by NaBH₄ through the electron transfer process is established in the present study.     

Microwave-assisted green synthesis of 4,5-dihydro-1<Emphasis Type="Italic">H</Emphasis>-pyrazole-1-carbothioamides in water

Rapid, efficient, simple and green procedure for the synthesis of 4,5-dihydro-1H-pyrazole-1-carbothioamides via the multicomponent reaction of aryl aldehydes, acetophenones and thiosemicarbazide in water in the presence of tetrabutylammonium hydroxide under microwave irradiation is reported.     

A multicomponent approach to the synthesis of 1,3-dicarbonylic compounds

A general synthesis of 1,3-dicarbonylic compounds using multicomponent reactions of isocyanides is described. The process involves a Passerini three-component condensation of glyoxal derivatives, isocyanides and acetic acid, followed by metal mediated reductive or solvolytic removal of the acid component. Noteworthy, reductive deacetoxylation of Passerini glyoxylamide adducts was successfully achieved using photochemically activated SmI₂. This procedure constitutes a novel convenient method for the direct synthesis of malonic retro-peptidic subunits.     

Recent development of two chitinase inhibitors,Argifin and Argadin,produced by soil microorganisms

Chitin, the second most abundant polysaccharide in nature, occurs in fungi, some algae and many invertebrates, including insects. Thus, chitin synthesis and degradation could represent specific targets for fungicides and insecticides. Chitinases hydrolyze chitin into oligomers of N-acetyl-d-glucosamine at key points in the life cycles of organisms, consequently, chitinase inhibitors have become subject of increasing interest. This review covers the development of two chitinase inhibitors of natural origin, Argifin and Argadin, isolated from the cultured broth of microorganisms in our laboratory. In particular, the practical total synthesis of these natural products, the synthesis of lead compounds via computer-aided rational molecular design, and discovery methods that generate only highly-active compounds using a kinetic target(chitinase)-guided synthesis approach (termed in situ click chemistry) are described.     

Chirality of molecular nanostructures on surfaces via molecular assembly and reaction: manifestation and control

The formation of chiral nanostructures via molecular assembly and reaction on solid surfaces is a ubiquitous surface process due to the symmetry-breaking at 2D surface. Studying chirality during the adsorption, assembly, and reaction of molecules on 2D solid surfaces at molecular level not only sheds deep insights into the enantioselective heterogeneous catalysis, chiral recognition, origin and evolution of chirality, and many important physical chemistry processes but also provides an important strategy to create chiral nanostructures. Here, we give a survey of recent advances in chiral expression and control in molecular assemblies and reactions on surfaces. We firstly give a brief introduction to the general concepts of chiral molecular nanostructures on surfaces. And then we focus on the induction and control of chirality expressed in molecular assemblies. The recent developments in the control strategies such as chiral co-adsorber, chiral auxiliary, chiral solvent, chiral templated surfaces, as well as the underlying mechanism to achieve the chiral induction and amplification, are reviewed. After that, we review the studies of chirality expressed in on-surface synthesis which has been proved to be a promising strategy to fabricate covalently bonded low-dimensional nanostructures and materials. In this respect, we introduce the chiral expression in the intramolecular and intermolecular coupling reactions on surfaces. In addition, we survey the methods to steer the stereoselectivity of on-surface reactions including the design of precursor structure, steric hindrance effect, substrate, kinetic parameters et al. Finally, the future outlook in this field is discussed.     

Recent progress of isocyanide-based multicomponent reactions in Iran

The aim of this review is to provide an overview of the contributions and recent advances made by Iranian scientists in the field of isocyanide-based reactions between 1999 and 2009. With over 100 publications during this period, Iranians are responsible for approximately 10% of all publications in the world involving isocyanide-based multicomponent reactions (IMCRs). Some important aspects of these IMCRs include the execution of reactions in green reaction mediums like water or ethanol, high atom economies, mild reaction conditions, high yields, and catalyst-free processes. On the other hand, in most of these reactions, new classes of heterocyclic compounds with potential biological and medicinal activities have been reported.     

Application of computer assisted combinatorial chemistry in antivirial,antimalarial and anticancer agents design

Combinatorial chemistry and technologies have been developed to a stage where synthetic schemes are available for generation of a large variety of organic molecules. The innovative concept of combinatorial design assumes that screening of a large and diverse library of compounds will increase the probability of finding an active analogue among the compounds tested. Since the rate at which libraries are screened for activity currently constitutes a limitation to the use of combinatorial technologies, it is important to be selective about the number of compounds to be synthesized. Early experience with combinatorial chemistry indicated that chemical diversity alone did not result in a significant increase in the number of generated lead compounds. Emphasis has therefore been increasingly put on the use of computer assisted combinatorial chemical techniques. Computational methods are valuable in the design of virtual libraries of molecular models. Selection strategies based on computed physicochemical properties of the models or of a target compound are introduced to reduce the time and costs of library synthesis and screening. In addition, computational structure-based library focusing methods can be used to perform in silico screening of the activity of Compounds against a target receptor by docking the ligands into the receptor model. Three case studies are discussed dealing with the design of targeted combinatorial libraries of inhibitors of HIV-1 protease, P. falciparum plasmepsin and human urokinase as potential antivirial, antimalarial and anti-cancer drugs. These illustrate library focusing strategies.     

Ultrasound promoted Barbier reactions and Csp3–Csp2 Stille coupling for the synthesis of diarylmethanes and substituted benzophenones

Here we present the preparation of a variety of diarylmethanes obtained via ultrasound Stille coupling under palladium catalysis between some substituted aryl compounds and benzyltributyltin compounds generated through sonicated Barbier reaction in a very short time reaction and excellent yield. The study reported below compares different methods to optimize the synthesis of usually unstable benzyltin derivatives and is another contribution to the investigation of Csp³–Csp² coupling process involving benzyl–aryl reagents. Substituted carboxylated benzophenones were easily prepared in a very good yield by oxidation of some diarylmethanes.     

三核铁钌簇配位取代反应的紫外与红外光谱研究

利用紫外光谱和红外光谱研究了十二羰基三铁和十二羰基三钌分别与二苯基乙炔和三苯基膦的配位取代反应。谱图数据揭示出原始物质消失和新物质形成过程，并对结果产物作了压片红外光谱测定，进一步证实了新物质的生成。     

Recent advances in the development of polycyclic skeletons via Ugi reaction cascades

Isocyanide-based multicomponent reactions are among the most powerful synthetic tools available. Particularly, the isocyanide-based Ugi reaction can allow rapid preparation of \(\alpha \)-aminoacyl amide derivatives and polyazaheterocycles with extensive pharmaceutical applications. Moreover, bridged polyazaheterocycles, including one or more quaternary carbon centers, can be constructed via the Ugi cascade reaction in a few steps. This review will emphasize synthesis and bioactivities of bridged compounds with quaternary centers constructed through Ugi cascade reactions.     

Multiactivation of organic reactions high pressure cycloaddition reactions catalyzed by lanthanides

Abstract

Combination of lanthanide catalysis and high pressure is highly beneficial in the Diels-Alder addition of ethyl vinyl ether to unsaturated keto compounds. The method is particularly appropriate for the synthesis of sterically congested dihydropyrans. The activation volumes of catalyzed and thermal hetero-Diels-Alder reactions do not differ significantly. This means conservation of the pericyclic character of the process.