Synthetic Organic Reactions Research Articles

Poly(vinylsulfonic acid)-grafted solid catalysts: new materials for acid-catalysed organic synthetic reactions

The synthesis, characterisation and application of novel high-density poly(vinylsulfonic acid)-grafted solid acid catalysts are described. A graft, radical polymerization procedure was employed, allowing the immobilisation of the acid form of vinylsulfonic acid monomer onto various carrier materials, such as polystyrene, silica or polysaccharide-based gels. The highest acid-exchange capacity (as determined by acid–base titration methods) achieved with these new materials was 5.2 mmol H+ g−1. The properties of these PVS-grafted materials as solid state acid catalysts have been examined from several perspectives, including their fundamental properties as materials with extremely high acid dissociation characteristics, their structural features as revealed from IR and solid-state NMR measurements, their thermal stability properties, and their surface morphologies, humidity dependencies and functionality. Compared to many other types of acid catalysts, these high-density poly(vinylsulfonic acid)-grafted materials demonstrated superior catalytic performance in esterification, Friedel–Crafts acylation, and condensation reactions. Moreover, these novel materials show high stability, significant anticorrosion capability and can be easily recycled.

Design of Sophisticated Bidentate Lewis Acids and Organocatalysts for Fine Organic Synthesis

Abstract Apart from enzymes as biocatalysts, a broad repertoire of chiral reagents, auxiliaries, and catalysts have been developed in recent years. In this respect, the design of new catalysts and new reactions in an efficient manner is increasingly important in this century for the construction of new and useful molecules. Accordingly, by designing and synthesizing sophisticated metal and non-metal catalysts, hitherto unattainable, unusual reactivity and selectivity is pursued in synthetic organic reactions. For example, the rational design of designer Lewis acids, particularly bidentate Lewis acid catalysts and their application to selective organic synthesis is carried out. In addition, the design of chiral phase transfer catalysts, chiral bifunctional organocatalysts, and chiral Brønsted acid catalysts as promising organocatalysts is realized for their application to practical asymmetric synthesis.

Importance of C−N Bond Rotation in N-Acyl Oxazolidinones in their SmI2-Promoted Coupling to Acrylamides

A detailed mechanistic investigation was undertaken to determine the dominating factors of the postelectron transfer steps in the SmI(2)-promoted carbon-carbon bond forming reaction between N-acyl oxazolidinones and acrylamides. Competition experiments were performed by reacting two N-acyl oxazolidinones with a limiting amount of N-t-butyl acrylamide, and from the product distribution, the relative reactivity values (RV) for a series of N-acyl oxazolidinones were then calculated against N-pivaloyl oxazolidinone as the reference. An almost linear correlation was obtained for the simple alkyl N-acyl oxazolidinones when ln RV was plotted against the activation barriers for C-N bond rotation (s-trans to s-cis) obtained by DFT calculations, implying that C-N bond rotation from the s-trans to s-cis conformation is one of the essential parameters controlling the reactivity. These results were substantiated by other competition experiments carried out for the corresponding imide derivatives, where rotation is not necessary for obtaining bidentate coordination and where no such correlation as described above was observable. The finding that the reactivity of the simple N-acyl oxazolidinones for these SmI(2)-mediated transformations correlates with the activation barriers for C-N bond rotation may have implications for other useful synthetic organic reactions involving similar substrates. Finally, these studies were extrapolated to understanding the poor reactivity of N-acyl oxazolidinones, as those derived from Evans chiral auxiliaries, with N-tert-butyl acrylamide. These couplings appear to be dominated by the activation energy for addition because of arising syn-pentane interactions in the transition-state for C-C bond formation. We demonstrate that the addition of Lewis acids can have a beneficial effect on the coupling yields.

還元晶析法による銀ナノ粒子と酸化チタン光触媒の複合化

Much interest has been taken in crystallizing silver nano-particles on metal oxide, for the purpose of using their composite as a noble catalyst for synthetic organic reactions. We studied crystallization of silver nano-particles onto TiO2photocatalyst with the help of reducible action of ethanol. Reducible action of ethanol was regulated by dosing with moisture, in order to crystallize silver nano-particles by heterogeneous nucleation. 1 wt%-Ag/TiO2 composite was prepared at reflux of ethanol in the presence of 5 vol% moisture with the result that size of Ag particles crystallized on surface of TiO2 averaged 12.4 nm. At that time, the reduction of Ag cation was completed for 1h. In the presence of 10 vol% moisture, the reduction ratio was 90% after 1 h of the crystallizing operation, and average size of the crystallized Ag particles was 8.8 nm. Photocatalytic activity of 1 wt%-Ag/TiO2 composite was enhanced with a decrease in size of the crystallized silver particles. For the preparation of 5 wt%-Ag/TiO2, 25 vol% moisture was required to crystallize silver nano-particles that brought about marked promotion of the photocatalytic activity. Further, the effect of reduction temperature on the crystallization of silver nano-particles was investigated in order to enhance photocatalytic activity of 7 wt%-Ag/TiO2.

ChemInform Abstract: Development of New Synthetic Organic Reactions Using Stannyl Radicals as Key Intermediates

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Opportunities Abound

Chemistry, both as a basic as well as an applied science, is of fundamental importance to our society. From food to clothing, from construction materials to nanoelectronics, from drugs to dyes, from cars to molecular machines; nothing would be possible without modern chemistry. Although not fully recognized by most people, chemistry is clearly one of the major technologies that have improved drastically the quality of our daily life. Nevertheless, despite the advances made, our science still offers significant challenges for the coming years. I am convinced that chemistry will also play a major role to provide solutions for the crucial problems of the next century: Contributions to the use of alternative energy supplies (hydrogen technology, fuel cells, biomass to liquid, etc.). The introduction of CO2-neutral raw materials for the chemical industry (use of renewable resources, carbon dioxide as a C1 building block, etc.). The development of new pharmaceuticals (against Alzheimer's disease, cancer, HIV) and the enabling of new materials (performance polymers), molecular electronics, and more. And last but not least, more sustainable processes for the production of bulk and fine chemicals (aniline, phenol, caprolactam, propylene oxide, polyurethanes, etc.). What does all of this have to do with ChemSusChem? This new journal, which you are now reading, is devoted in a broad sense to the development of a more sustainable chemistry. Sustainability is the key subject of all the goals mentioned above. ChemSusChem aims to bring together leading chemists from different fields to present their latest accomplishments and delineate the challenges for the future of the important and exiting aspects of sustainability. A glance at the content of the first issue reveals already the broad nature of the field, from improved catalytic methods to applications of renewables, from the conversion of solar energy to research on fuel cells. The interdisciplinary nature of this journal offers interesting opportunities for its readers, and I hope that the scientific content will stimulate chemists from all areas to broaden their horizon and apply their specific knowledge towards sustainability. Whether your interests lie in synthetic organic chemistry, catalysis, energy, environment, materials, renewables, or reaction engineering, we hope that you will enjoy reading ChemSusChem and discover for yourself the emerging state of the art of this exciting field of chemistry. Matthias Beller Rostock, Germany, January 2008

N-Alkylation of amines by photocatalytic reaction in a microreaction system

A photocatalytic microreaction system was developed and photocatalytic N-alkylation process of benzylamine, aniline, and piperidine was examined. The reaction proceeded quite rapidly in the microreactors with immobilized Pt-free TiO 2 as well as Pt-loaded TiO 2, while it has been reported that the N-alkylation did not occur by the irradiation of Pt-free TiO 2 in conventional batch reactors. It was revealed that by using the unique features of the continuous-flow microreactor, for instance spatial illumination homogeneity and precise control of flow and irradiation conditions, one can control the selectivity of N-alkylation and N, N-dialkylation processes. These results suggest the possibilities of a photocatalytic microreaction system on organic synthetic reactions.

Development of New Synthetic Organic Reactions Using Stannyl Radicals as Key Intermediates

Development of New Synthetic Organic Reactions Using Stannyl Radicals as Key Intermediates

有機ホウ素化合物の触媒的有機合成化学

In this review, particular attention will be given to the synthesis of organoboron compounds via the metal-catalyzed addition and coupling reactions, and their synthetic applications in organic syntheses. The traditional methods for the synthesis of organoboron compounds are based on the reaction of trialkyl borates with Grignard or lithium reagents (transmetalation) or the addition of H-B reagents to alkenes or alkynes (uncatalyzed hydroboration). Although these methods are now most common and convenient for large-scale preparations, the metal-catalyzed reactions are advantageous in terms of efficiency and selectivity of the transformations. Hydroboration of alkenes and alkynes is one of the most studied of reactions in the synthesis of organoboron compounds and their application to organic synthesis. However, the catalyzed hydroboration to be a more interesting strategy to realize the different chemo-, regio-, diastereo-, and enantioselectivities, relative to the uncatalyzed reaction. The cross-coupling reaction of metal-boryl reagents is an alternative to the transmetalation method and perhaps a more convenient and direct protocol for the synthesis of organoboron compounds from organic halides and aromatic C-H bond. Much attention has been recently focused on organoboronic acids and their esters due to their practical usefulness for synthetic organic reactions including asymmetric synthesis, combinatorial synthesis, and polymer synthesis, molecular recognition such as host-guest compounds, and neutron capture therapy in treatment of malignant melanoma and brain tumor. New synthetic procedures reviewed in this article will serve to find further applications of organoboron compounds.

SUPPORTED CROSS-METATHESIS

OLEFIN CROSS-METATHESIS , the coupling of two distinct alkenes, is a useful synthetic organic reaction, but it has only rarely been achieved on solid phase. Researchers have now found that proper spacing between the polymer support and the tethered alkene makes the solid-phase reaction more feasible. Solid-phase synthesis is used to construct diverse small-molecule libraries in an automated fashion, allowing easy removal of by-products and excess reagents from reaction mixtures. The finding could aid the use of olefin cross-metathesis in discovering compounds with novel bioactivities. Kazunori Koide, assistant professor of chemistry at the University of Pittsburgh, and graduate student Amanda L. Garner found that increasing the distance between the polymer and the support-bound olefin in olefin cross-metathesis reactions leads to higher product yields ( Org. Lett. , DOI: 10.1021/ol702415x). To apply their findings to diverse substrates, Koide and Garner constructed a novel solid support by attaching a lin...

Direct Analysis in Real Time for Reaction Monitoring in Drug Discovery

Direct analysis in real time (DART) is a novel ionization technique that provides for the rapid ionization of small molecules under ambient conditions. In this study, several commercially available drugs as well as actual compounds from drug discovery research were examined by LC/UV/ESI-MS and DART interfaced to a quadrupole mass spectrometer. For most compounds, the molecular ions observed by ESI-MS were observed by DART/MS. DART/MS was also studied as a means to quickly monitor synthetic organic reactions and to obtain nearly instantaneous molecular weight confirmations of final products in drug discovery. For simple, synthetic organic transformations, the trends in the intensities of the mass spectral signals for the reactant and product obtained by DART/MS scaled closely with those of the diode array or the total ion chromatogram obtained by LC/UV/ESI-MS. In summary, DART is a new tool that complements electrospray ionization for the rapid ionization and subsequent mass spectral analysis of compounds in drug discovery.

A synthetic classic reinvented

The Diels-Alder cycloaddition, a classic synthetic organic reaction, is now being harnessed to label proteins.

Recently Developed Organometallic Complexes of Zn, Cu(Zn, Li), Fe, Ru and Less-used Ions. Use in Selective 1,2-or 1,4-Additions, Transfer Hydrogenations, Aldol Reactions and Diels-Alder Reactions

This review introduces the broad general topic of asymmetric organic synthetic reactions and reagents. Reagents containing both frequently used metallic ions, e.g. Zn++, Cu+(++) and Ru++, and rarely used ions, such as Ag+, employed in the construction of designed chiral centers, are updated here. Enantioselective 1,2-additions and 1,4-conjugate additions, transfer hydrogenations, and diasteroselective aldol reaction are discussed. The selectivities induced by chiral β-, δ- or γ-chiral amino alcohols, chiral diols, chiral binaphthyl derivatives, chiral P,N-containing auxiliaries, and other ligands used to prepare chiral metallic complexes, were compared in each reaction system. The use of two or more metallic ions with a single chiral ligand has now become a more popular strategy to catalyze chiral-center-controlled processes. For example, only diethylzinc was used in enantioselective additions to aldehydes in early studies. Recently, the combination of Et2Zn and Cu++ in the selective additions has been used to achieve high ee% values and yields. Finally, quantum calculations have been used to obtain kinetic data to predict a reactions ee% values. For example, the calculated δGcal. values have a strong relationship with the obtained δGfit values which have the direct linkage with the ee% values.

Seasoning materials chemistry by using a well-matured organic concept.

The concept "introduction of allylic 1,3-strain (A(1,3)-strain) to photochromism" originated from the experience of total synthesis of natural products about 18 years ago, when the author was a post doc. It was first applied to synthetic organic reactions, then it was successfully employed in the diastereoselective photochromic reactions of diarylethenes. A diastereomeric excess of the photoreaction was 88 % for the first example, and it was improved to 94 % by the recent operation of rational molecular tailoring.

Hydrogen bond driven chemical reactions: Beckmann rearrangement of cyclohexanone oxime into epsilon-caprolactam in supercritical water.

Recent experiments have shown that supercritical water (SCW) has the ability to accelerate and make selective synthetic organic reactions, thus replacing the common but environmentally harmful acid and basic catalysts. In an attempt to understand the intimate mechanism behind this observation, we analyze, via first-principles molecular dynamics, the Beckmann rearrangement of cyclohexanone oxime into epsilon-caprolactam in supercritical water, for which accurate experimental evidence has been reported. Differences in the wetting of the hydrophilic parts of the solute, enhanced by SCW, and the disrupted hydrogen bond network are shown to be crucial in triggering the reaction and in making it selective. Furthermore, the enhanced concentrations of H(+) in SCW play an important role in starting the reaction.

Novel Synthetic Organic Reactions of Organotin Reagents Based on Tin‐Hetero Atom Bond

AbstractFor Abstract see ChemInform Abstract in Full Text.

Application of Lithium Naphthalene to Organic Synthetic Reactions

AbstractFor Abstract see ChemInform Abstract in Full Text.

Development of Novel Synthetic Organic Reactions: Synthesis of Antitumor Natural Products and Leading Compounds for New Pharmaceuticals

AbstractFor Abstract see ChemInform Abstract in Full Text.

スズ‐ヘテロ原子結合に基づく有機スズの新反応

スズ‐ヘテロ原子結合に基づく有機スズの新反応

Development of novel synthetic organic reactions: synthesis of antitumor natural products and leading compounds for new pharmaceuticals

Biologically active natural products with unique, highly complex molecular skeletons have been used as leading compounds for raw materials of new drugs. Due to the limitations of natural supply, highly efficient, large-scale syntheses and molecular design have been sought in drug discovery. For this purpose, we have focused on a synthetic strategy effective in developing novel reactions and reagents and found several useful regio- and stereospecific reactions, contributing to the synthesis of otherwise unattainable target molecules. The application of these reactions for the total synthesis of three types of potent cytotoxic natural products for the first time is described in this paper. The basic concept is first described. Then the total synthesis of anthracyclines, fredericamycin A, and discorhabdins is reported. Novel reactions using hypervalent iodine reagents under environmentally benign conditions are also described. The future prospects for this method are discussed.