Laboratoire de Chimie Organique

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The last few years have witnessed a spectacular advancement in new catalytic methods based on metal-free organic molecules. In many cases, these small compounds give rise to extremely high enantioselectivities. Preparative advantages are notable: usually the reactions can be performed under an aerobic atmosphere with wet solvents. The catalysts are inexpensive and they are often more stable than enzymes or other bioorganic catalysts. Also, these small organic molecules can be anchored to a solid support and reused more conveniently than organometallic/bioorganic analogues, and show promising adaptability to high-throughput screening and process chemistry. Herein we focus on four different domains in which organocatalysis has made major advances: 1) The activation of the reaction based on the nucleophilic/electrophilic properties of the catalysts. This type of catalysis has much in common with conventional Lewis acid/base activation by metal complexes. 2) Transformations in which the organic catalyst forms a reactive intermediate: the chiral catalyst is consumed in the reaction and requires regeneration in a parallel catalytic cycle. 3) Phase-transfer reactions: The chiral catalyst forms a host-guest complex with the substrate and shuttles between the standard organic solvent and the second phase (i.e. a solid, aqueous, or fluorous phase in which the organic transformation takes place). 4) Molecular-cavity-accelerated asymmetric transformations: the catalyst can select between competing substrates, depending on size and structure criteria. The rate acceleration of a given reaction is similar to the Lewis acid/base activation and is the consequence of the simultaneous action of different polar functions. Herein it is shown that organocatalysis complements rather than competes with current methods. It offers something conceptually novel and opens new horizons in synthesis.

ADVERTISEMENT RETURN TO ISSUEPREVArticleDendritic Catalysts and Dendrimers in CatalysisDidier Astruc and Françoise ChardacView Author Information Laboratoire de Chimie Organique et Organométallique, UMR CNRS N°5802, Université Bordeaux I, 33405 Talence Cedex, France Cite this: Chem. Rev. 2001, 101, 9, 2991–3024Publication Date (Web):August 17, 2001Publication History Received6 April 2001Published online17 August 2001Published inissue 1 September 2001https://pubs.acs.org/doi/10.1021/cr010323thttps://doi.org/10.1021/cr010323tresearch-articleACS PublicationsCopyright © 2001 American Chemical SocietyRequest reuse permissionsArticle Views5856Altmetric-Citations987LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Catalysis,Catalysts,Dendrons,Ligands,Redox reactions Get e-Alerts

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe Behavior of 1,n-Enynes in the Presence of Transition MetalsCorinne Aubert, Olivier Buisine, and Max MalacriaView Author Information Université Pierre et Marie Curie (Paris 6), Laboratoire de Chimie Organique de Synthèse, Tour 44−54; 2° étage, CC 229, 4, place Jussieu, 75252 Paris Cedex 05, France Cite this: Chem. Rev. 2002, 102, 3, 813–834Publication Date (Web):February 13, 2002Publication History Received7 August 2001Published online13 February 2002Published inissue 1 March 2002https://pubs.acs.org/doi/10.1021/cr980054fhttps://doi.org/10.1021/cr980054fresearch-articleACS PublicationsCopyright © 2002 American Chemical SocietyRequest reuse permissionsArticle Views6809Altmetric-Citations868LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Catalysts,Cyclization,Hydrocarbons,Isomerization,Metals Get e-Alerts

Abstract This technical report is a general introduction to organic photochromism. The definition of photochromism (PC) is given together with that of words with the ending "chromism", such as thermo-, electro-, piezo-, and tribochromism. Important concepts such as two-photon, gated, dual-mode PC and chirochromism are illustrated. The concept of fatigue (chemical degradation) and the determination of the main photochromic parameters (number of cycles, cyclability, half-life), and the spectrokinetic and mechanistic aspects are discussed. The main families of PC (organic compounds and biological receptors) are illustrated with chemical formulae, and the different types of reactions involved in the photochromic processes (pericyclic reactions, E / Z isomerization, group transfer, etc.) are listed. Some examples of applications to "optical power limiting" substances, photoresponsive materials, and photoswitchable biomaterials are considered.

In recent years, N-heterocyclic carbenes (NHC) have proved to be a versatile class of spectator ligands in homogeneous catalysis. Being robust anchoring functions for late transition metals, their ligand donor capacity and their molecular shape is readily modified by variation of the substituents at the N-atoms and the structure of the cyclic backbone. After the first attempts to use chiral NHC ligands in asymmetric catalysis in the late 1990's, which initially met with limited success, several novel structural concepts have emerged during the past two years which have led literally to an explosion of the field. With a significant number of highly selective chiral catalysts based on chiral NHCs having been reported very recently, several general trends in the design of new NHC-containing molecular catalysts for stereoselective transformations in organic synthesis emerge.

A general and efficient transfection procedure, based on compacted lipopolyamine-coated plasmids, has been developed. The active species is obtained by simple addition of excess synthetic lipospermine solution to the DNA and binds within minutes to the cell membrane. This technique has been developed on endocrine cells of the intermediate lobe of the pituitary as a general tool for physiological work on primary cells; it is not toxic and does not interfere with physiological regulations in melanotrope cells. A variety of eukaryotic cell cultures also have been transfected with success for transient and stable expression.

Multidisciplinary research on novel organic luminescent dyes is propelled by potential applications in plastic electronics and biomedical sciences. The construction of sophisticated fluorescent dyes around a tetrahedral boron(III) center is a particular approach that has fueled the creativity of chemists. Success in this enterprise has been readily achieved with simple synthetic protocols, the products of which display unusual spectroscopic behavior. This account is a critical review of recent advances in the field of boron(III) complexes (excluding BODIPYs and acetylacetonate boron complexes) involving species displaying similar coordination features, and we outline their potential development in several disciplines.

Currently available approaches to molecular-scale logic gates are summarized and compared. These include: chemically-controlled fluorescent and transmittance-based switches concerned with small molecules, DNA oligonucleotides with fluorescence readout, oligonucleotide reactions with DNA-based catalysts, chemically-gated photochromics, reversibly denaturable proteins, molecular machines with optical and electronic signals, two-photon fluorophores and multichromophoric transient optical switches. The photochemical principles of electron and energy transfer are involved in several of these approaches. More complex molecular logic systems with reconfigurability and superposability provide contrasts with current semiconductor electronics. Integration of simple logic functions to produce more complex ones is also discussed in terms of recent developments.

Mild, efficient, copper-catalyzed N-arylation procedures for nitrogen heterocycles, amides, carbamates, and C-arylation procedures for malonic acid derivatives have been developed that afford high yields of arylated products with excellent selectivity. The N-arylation of imidazole with aryl bromides or iodides was found to be greatly accelerated by inexpensive, air-stable catalyst systems, combining catalytic copper salts or oxides with a set of structurally simple chelating ligands. The reaction was shown to be compatible with a broad range of aryl halides, encompassing sterically hindered, electron-poor, and electron-rich ones, providing the arylated products under particularly mild conditions (50-82 degrees C). The lower limit in ligand and catalyst loading and the scope of Ullmann-type condensations catalyzed by complexes bearing those ligands with respect to the nucleophile class have also been investigated. Chelating Schiff base Chxn-Py-Al (1c) generates a remarkably general copper catalyst for N-arylation of pyrrole, indole, 1,2,4-triazole, amides, and carbamates; and C-arylation of diethyl malonate, ethyl cyanoacetate, and malononitrile with aryl iodides under mild conditions (50-82 degrees C). The new method reported here is the most successful to date with regard to Ullmann-type arylation of some of these nucleophiles.

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For the linear triatomic X–H··· system, the separability of the X–H stretching vibrations from the hydrogen bond vibrations is analyzed in the spirit of the adiabatic approximation. The adiabatic wavefunctions for X–H stretching vibrations are shown to be suitable functions for the evaluation of the principal factors determining the infrared spectral properties of the actual species of carboxylic acid dimers and imidazole crystal. Theoretical infrared spectra in the X–H stretching region of these systems are then obtained and compared with the experimental ones. The quantitative reconstitution of the experimental spectra and, in particular, the predictions for the effect of isotopic substitution of H by D are confirmed. The principal features of the unusual spectral properties of the X–H stretching vibrations in hydrogenbonded systems seem therefore to result from a somewhat peculiar coupling mechanism suggested in the theory.

A 3-azidoproflavine derivative was covalently linked to the 5'-end of an octathymidylate synthesized with the [alpha]-anomers of the nucleoside. Two target nucleic acids were used for this substituted oligo-[alpha]-thymidylate: a 27-mer single-stranded DNA fragment containing an octadeoxyadenylate sequence and a 27-mer duplex containing eight contiguous A.T base pairs with all adenines on the same strand. Upon visible light irradiation the octa-[alpha]-thymidylate was photocrosslinked to the single-stranded 27-mer. Chain breaks were induced at the crosslinked sites upon piperidine treatment. From the location of the cleavage sites on the 27-mer sequence it was concluded that a triple helix was formed by the azidoproflavine-substituted oligo-[alpha]-thymidylate with its complementary oligodeoxyadenylate sequence. When the 27-mer duplex was used as a substrate cleavage sites were observed on both strands after piperidine treatment of the irradiated sample. They were located at well defined positions which indicated that the octathymidylate was bound to the (dA)8.(dT)8 sequence in parallel orientation with respect to the (dA)8-containing strand. Specific binding of the [alpha]-octathymidylate involved local triple strand formation with the duplex (dA)8.(dT)8 sequence. This result shows that it is possible to synthesize sequence-specific molecules which specifically bind oligopurine-oligopyrimidine sequences in double-stranded DNA via recognition of the major groove hydrogen bonding sites of the purines.

Abstract Clays have long been used as catalysts [1] and they retain a continuing important role since they constitute the matrix of many industrial catalysts based on zeolites. Intercalated clays are a new class of materials, in which an homogeneous distribution of micropores can be obtained with pore openings varying from 4 Å to 18 Å according to the type of pillars. These solids are then attractive because they can adsorb and convert large molecules.

The reactions reviewed herein are those showing an unusual outcome when performed in water or in an aqueous medium. Notably, transformations are included for which the hydrophobic effect might be invoked as the activation factor, as well as cases where water leads to valuable changes compared to traditional solvents, except when they are clearly due to the polarity as for example in nucleophilic substitution reactions and except when the effect comes from the addition of a few equivalents of water. 1. Introduction 2. Physicochemical Background 2.1 Structure of Water 2.2 Aqueous Solutions of Simple Molecules 2.3 Hydrophobic Effects 2.4 Reactivity in Water 3. Pericyclic Reactions 3.1 Diels-Alder Reactions 3.2 Hetero Diels-Alder Reactions 3.3 Dipolar Cycloadditions 3.4 Claisen Rearrangements 4. Nucleophilic Additions 4.1 Aldolisation (Mukaiyama Reaction) 4.2 Michael-Type Reactions 4.3 Other Nucleophilic Additions 5. Organometallic Chemistry 5.1 Barbier-Type Reactions 5.2 Transition Metal Complex Catalyzed Reactions 5.3 Other Metal-Catalyzed Reactions 6. Oxidations 7. Reductions 8. Photochemistry 9. Conclusion

ADVERTISEMENT RETURN TO ISSUEPREVReviewCopper-Catalyzed Diels−Alder ReactionsSébastien Reymond* and Janine Cossy*View Author Information Laboratoire de Chimie Organique, ESPCI ParisTech, CNRS, 10 Rue Vauquelin, 75231 Paris Cedex 05, France* To whom correspondence should be addressed. E-mail: [email protected]. Tel: (+33) 1 40 79 44 29. Fax: (+33) 1 40 79 46 60.Cite this: Chem. Rev. 2008, 108, 12, 5359–5406Publication Date (Web):October 23, 2008Publication History Received12 February 2008Published online23 October 2008Published inissue 10 December 2008https://pubs.acs.org/doi/10.1021/cr078346ghttps://doi.org/10.1021/cr078346greview-articleACS PublicationsCopyright © 2008 American Chemical SocietyRequest reuse permissionsArticle Views18049Altmetric-Citations373LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Addition reactions,Adducts,Catalysts,Ligands,Stereoselectivity Get e-Alerts

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTThe Dendritic Effect in Molecular Recognition: Ferrocene Dendrimers and Their Use as Supramolecular Redox Sensors for the Recognition of Small Inorganic AnionsChristine Valério, Jean-Luc Fillaut, Jaime Ruiz, Joëlle Guittard, Jean-Claude Blais, and Didier AstrucView Author Information Laboratoire de Chimie Organique et Organométallique URA CNRS No. 35, Université Bordeaux I, 351 Cours de la Libération, 33405 Talence Cédex, France Laboratoire de Chimie Structurale Organique et Biologique, EP 103, Université Paris VI, Place Jussieu 75252 Paris Cédex 05, France Cite this: J. Am. Chem. Soc. 1997, 119, 10, 2588–2589Publication Date (Web):March 12, 1997Publication History Received2 December 1996Published online12 March 1997Published inissue 1 March 1997https://pubs.acs.org/doi/10.1021/ja964127thttps://doi.org/10.1021/ja964127trapid-communicationACS PublicationsCopyright © 1997 American Chemical SocietyRequest reuse permissionsArticle Views1714Altmetric-Citations390LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Anions,Dendrons,Redox reactions,Sandwich compounds,Titration Get e-Alerts

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSelective Preparation of Complex Polycyclic Molecules from Acyclic Precursors via Radical Mediated- or Transition Metal-Catalyzed Cascade ReactionsMax MalacriaView Author Information Laboratoire de Chimie Organique de Synthèse, Université Pierre et Marie Curie (Paris VI), URA CNRS 408, Tour 44-54, B.P 229, 4 Place Jussieu, 75252 Paris Cedex 05, France Cite this: Chem. Rev. 1996, 96, 1, 289–306Publication Date (Web):February 1, 1996Publication History Received10 July 1995Revised29 September 1995Published online1 February 1996Published inissue 1 January 1996https://pubs.acs.org/doi/10.1021/cr9500186https://doi.org/10.1021/cr9500186research-articleACS PublicationsCopyright © 1996 American Chemical SocietyRequest reuse permissionsArticle Views3031Altmetric-Citations392LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Cyclization,Mixtures,Organic reactions,Precursors,Stereoselectivity Get e-Alerts

The hydrosilylation reaction enables the production of silicon polymers. Platinum-carbene complexes are reported that catalyze the hydrosilylation reaction of alkenes with remarkable efficiency and exquisite selectivity and avoid the formation of platinum colloids. By-products, typically encountered with previous catalytic systems, are suppressed with these platinum derivatives.

T cell IL-17 displays proinflammatory properties and is expressed in the synovium of patients with rheumatoid arthritis. Its contribution to the arthritic process has not been identified. Here, we show that blocking of endogenous IL-17 in the autoimmune collagen-induced arthritis model results in suppression of arthritis. Also, joint damage was significantly reduced. In contrast, overexpression of IL-17 enhanced collagen arthritis. Moreover, adenoviral IL-17 injected in the knee joint of type II collagen-immunized mice accelerated the onset and aggravated the synovial inflammation at the site. Radiographic and histologic analysis showed markedly increased joint destruction. Elevated levels of IL-1beta protein were found in synovial tissue. Intriguingly, blocking of IL-1alphabeta with neutralizing Abs had no effect on the IL-17-induced inflammation and joint damage in the knee joint, implying an IL-1 independent pathway. This direct potency of IL-17 was underscored in the unabated IL-17-induced exaggeration of bacterial cell wall-induced arthritis in IL-1beta(-/-) mice. In conclusion, this data shows that IL-17 contributes to joint destruction and identifies an IL-1-independent role of IL-17. These findings suggest IL-17 to be a novel target for the treatment of destructive arthritis and may have implications for tissue destruction in other autoimmune diseases.