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Productions scientifiques

Nechab, Malek.

ACL - Articles dans des revues à comité de lecture

26 références.

  • Abdallah, M.; Al Mousawi, A.; Nechab, M.; Hijazi, A.; Fouassier, J. - P.; Dumur, F.; Lalevee, J. Chemphotochem 2019, 3 (11), 1162-1170.
    Résumé : Diethoxyacetate salts are investigated as new co-initiators for the free radical polymerization (FRP) of (meth)acrylates upon visible light exposure, with light emitting diodes (LEDs; 405 nm, 477 nm) being employed for this purpose. Interestingly, the impact of the counter cation on their initiating ability is clearly highlighted. When these co-initiators are combined with commercial photoinitiators such as 2-isopropylthioxanthone (ITX) or camphorquinone (CQ), good to excellent free radical polymerization initiating performances are found and high final reactive function conversions are achieved. In the absence of these co-initiators, no or poor polymerization occurs, clearly highlighting the importance of these co-initiators for an efficient process. These systems can be interesting for the replacement of aromatic amines opening the way for amine-free Type II photoinitiating systems.

  • Pigot, C.; Noirbent, G.; Bui, T. - T.; Peralta, S.; Gigmes, D.; Nechab, M.; Dumur, F. Materials 2019, 12 (8), 1342.
    Résumé : A series of ten push-pull chromophores comprising 1H-cyclopenta[b]naphthalene-1,3(2H)-dione as the electron-withdrawing group have been designed, synthesized, and characterized by UV-visible absorption and fluorescence spectroscopy, cyclic voltammetry and theoretical calculations. The solvatochromic behavior of the different dyes has been examined in 23 solvents and a positive solvatochromism has been found for all dyes using the Kamlet-Taft solvatochromic relationship, demonstrating the polar form to be stabilized in polar solvents. To establish the interest of this polyaromatic electron acceptor only synthesizable in a multistep procedure, a comparison with the analog series based on the benchmark indane-1,3-dione (1H-indene-1,3(2H)-dione) has been done. A significant red-shift of the intramolecular charge transfer band has been found for all dyes, at a comparable electron-donating group. Parallel to the examination of the photophysical properties of the different chromophores, a major improvement of the synthetic procedure giving access to 1H-cyclopenta[b]naphthalene-1,3(2H)-dione has been achieved.

  • Pigot, C.; Noirbent, G.; Peralta, S.; Duval, S.; Nechab, M.; Gigmes, D.; Dumur, F. Helvetica Chimica Acta 2019.
    Résumé : An unprecedented nucleophilic addition of piperidine on an electron acceptor, namely, 2-(3-oxo-2,3-dihydro-1H-cyclopenta[b]naphthalen-1-ylidene)malononitrile is reported. This unexpected behavior was observed during the synthesis of push-pull dyes using the classical Knoevenagel reaction. To overcome this drawback, use of diisopropylethylamine (DIPEA) enabled to produce the expected dyes PP1 and PP2. The optical and electrochemical properties of the different dyes were examined. Theoretical calculations were also carried out to support the experimental results. To evidence the higher electron-withdrawing ability of this electron acceptor, a comparison was established with two dyes (PP3 and PP4) comprising its shorter analogue.

  • Arif, T.; Borie, C.; Jean, M.; Vanthuyne, N.; Bertrand, M. P.; Siri, D.; Nechab, M. Organic Chemistry Frontiers 2018, 5 (5), 769-776.
    Résumé : Propargylic carbonates were converted to indenes through a S(N)2/Alder-ene cascade triggered by organocopper reagents. The reaction tolerates different organocopper species generated either from organolithiums or Grignard reagents. A catalytic version of this strategy could be devised using either copper or iron catalysts. Attempts to transfer chirality from an enantioenriched substrate revealed a moderate chirality conversion because of a low discrimination between the two faces of the internal olefinic partner with these typical substrates. The theoretical investigation supports a concerted closed-shell mechanism and highlights the influence of the substituents on the activation parameters and on the synchronicity of C-H bond breaking and C-C bond forming during the Alder-ene step.
    Mots-clés : allenes, c-h functionalization, cascade rearrangements, chemical-reactions, chirality, enantioselective synthesis, ene reaction, indenes, insertion reactions, n-alkyl radicals.

  • Borie, C.; Mondal, S.; Arif, T.; Briand, M.; Lingua, H.; Dumur, F.; Gigmes, D.; Stocker, P.; Barbarat, B.; Robert, V.; Nicoletti, C.; Olive, D.; Maresca, M.; Nechab, M. European Journal of Medicinal Chemistry 2018, 148, 306-313.
    Résumé : A novel series of enediynes possessing pentafluorophenylsulfoxide have been developed. The innovative compounds possess antiproliferative activity against a broad panel of human cancer cells originating from breast, blood, lung, kidney, colon, prostate, pancreas or skin with IC50 ranging from 0.6 to 3.4 mu M. The antiproliferative activity of enediynes in darkness is associated to their ability to compromise microtubule network. In addition, exposure to UV leads to double-stranded DNA cleavage caused by the newly synthesized molecules reducing further their IC50 in nanomolar range against human tumor cells, including chemo-resistant pancreatic cancer cells. Taken together, the examined data demonstrate that enediynes possessing pentafluorosulfoxide are promising molecules in the cancer therapy. (C) 2018 Elsevier Masson SAS. All rights reserved.
    Mots-clés : Anticancer, bergman cyclization, cleavage, DNA cleavage, Enediynes, hypoxic tumors, in-vivo, Light activation, lysine, Microtubules, pancreatic-cancer, ph-gated transitions, photocleavage, selectivity, sulfones.

  • Garra, P.; Dumur, F.; Gigmes, D.; Nechab, M.; Morlet-Savary, F.; Dietlin, C.; Gree, S.; Fouassier, J. P.; Lalevee, J. Macromolecules 2018, 51 (7), 2706-2715.
    Résumé : Free radical polymerization (FRP) initiation from metal acetylacetonate-bidentate ligand interaction (MABLI) under mild conditions (room temperature, under air) is discussed here for different metal centers (Mn, V, and Cu). First, without light, in MABLI systems such as V(acac)(3)/2-diphenylphosphinobenzoic acid (2dppba), Mn(acac)(3)/2dppba, or Cu(acac)(2)/2dppba, electron-rich aryl (Ar-center dot) radicals were conveniently and efficiently produced by the reaction of electron-poor acac(center dot) radicals with the iodonium salt (Iod), leading to an enhancement of pure redox (no light) polymerizations. Second, it was found that V(III)*/Iod reaction is generating aryl (Ar-center dot) radicals at a high enough rate to initiate a photopolymerization process upon mild irradiation (LED@405 nm). This reaction can be implemented in redox photoactivated systems (e.g., using three-component V(acac)(3)/2dppba/Iod systems) in order to spectacularly enhance a slow redox process from 40 degrees C exothermicity in 800 s to 93 degrees C in less than 200 s. Third, an impressive chemical bleaching (without light) was reported for the Mn(acac)(3)/2dppba reaction. Photoactivation of the Mn(acac)(3)/2dppba/Iod system led to outstanding FRP initiation efficiencies (<20 s for more than 85% C=C conversion of a low-viscosity methacrylate resin). Light enhancement of surface curing was confirmed for all the redox photoactivated polymerizations using Raman confocal microscopy. Overall, amine-free peroxide-free MABLI radical initiating systems were highly improved for safer and even more efficient redox (photoactivated) polymerizations. This original combination of redox polymerization and photopolymerization will be highly worthwhile to combine in one approach the advantages of both techniques.
    Mots-clés : 3d printing resins, cationic-polymerization, confocal raman microscopy, dental resins, initiating systems, oxygen inhibition, photoinitiating systems, photopolymerization processes, reactivity, shadow areas.

  • Garra, P.; Dumur, F.; Nechab, M.; Morlet-Savary, F.; Dietlin, C.; Graff, B.; Doronina, E. P.; Sidorkin, V. F.; Gigmes, D.; Fouassier, J. - P.; Lalevee, J. Macromolecules 2018, 51 (16), 6395-6404.
    Résumé : New peroxide-free, amine-free, and phosphine-free redox free radical polymerization (RFRP) initiating systems comprising remarkably stable (i) metal acetylacetonates (Mn(acac)(3), Cu(acac)(2)) and (ii) carbonyl compounds bearing labile hydrogen in the alpha-position are presented for polymerization initiation under mild conditions (under air, at room temperature, nonpurified monomers). The systems proposed in this work are competitive or even outranked the well-known peroxide-based RFRP reference in several criteria: (i) toxicity, (ii) stability, (iii) surface curing, (iv) overall double-bond conversions, and (v) workability of the RFRP mixture (longer gel times are now possible). Radical initiating reactions are studied using many complementary experimental/theoretical techniques: optical pyrometry, thermal imaging, Raman confocal microscopy, electron spin resonance (ESR), ESR spin trapping (ESR-ST), high-resolution electrospray ionization mass spectrometry (HR-ESI-MS), density functional theory (DFT), simulations of bond dissociation energies (BDE), reaction enthalpies, and DFT simulations of seven unknown ESR-ST adducts. A full consistent picture of the chemical mechanisms involved in these new redox systems is provided.
    Mots-clés : alkyd paints, confocal raman microscopy, dental resins, initiating systems, ligand interaction mabli, manganese tris(acetylacetonate)-acetic acid, monitoring photopolymerization reactions, organic halides, shadow areas, translucent fiberglass post.

  • Garra, P.; Dumur, F.; Nechab, M.; Morlet-Savary, F.; Dietlin, C.; Graff, B.; Gigmes, D.; Fouassier, J. - P.; Lalevee, J. Polymer Chemistry 2018, 9 (16), 2173-2182.
    Résumé : The use of new stable copper acetylacetonates in combination with specific bidentate ligands (e.g. 2dppba) is proposed for redox free radical polymerization (FRP) under mild reaction conditions (under air and at room temperature). These systems show high performances so that they can compete with the well-established reference redox initiating systems based on the amine/benzoylperoxide combination. Remarkably, some of our systems are also highly efficient when excited in the near infrared region (NIR), demonstrating that our redox systems can also be activated by light. Using this strategy, the initial redox free radical polymerization could be converted into a redox photoactivated one. More interestingly, a stable copper methacryloyloxy-ethylacetoacetate (Cu(AAEMA)(2)) bearing a reactive methacrylate function and a copper acetylacetonate moiety could be used to polymerize a first polymer layer onto which a second polymerization could be carried out. Precisely, the second polymerization was initiated by a redox process using mild reaction conditions (at room temperature and under air), different from the process used to form the underlayer. To the best of our knowledge, this re-initiation of polymerization from a pre-polymerized layer by a second polymerization technique is highly original and is of crucial industrial/academic interest as no high energy consumption/harmful wavelengths are required to reinitiate the polymerization. The efficiency of this strategy is illustrated by grafting from a 3D printed object.
    Mots-clés : chemistry, complex, composites, confocal raman microscopy, initiating systems, photoinitiating systems, photopolymerization processes, polymers, resins, shadow areas.

  • Mouysset, D.; Tessonnier, C.; Tintaru, A.; Dumur, F.; Jean, M.; Vanthuyne, N.; Bertrand, M. P.; Siri, D.; Nechab, M. Chemistry-a European Journal 2017, 23 (35), 8375–8379.
    Résumé : Enantioenriched indenes were reached through a chirality conversion strategy using original axially chiral benzylidene cyclanes. Good to high remote diastereocontrol and excellent enantiocontrol were observed in this cascade involving copper-catalyzed homologation of terminal alkynes, in situ allenoate formation and Alder-ene cyclization.
    Mots-clés : 1-methylcyclohexylidene-4-acetic acid, asymmetric synthesis, asymmetric-synthesis, bearing, c-h functionalization, carbocycles, catalyst, chirality, cyclization, enantioselective synthesis, ene reaction, enediynes, indanes.

  • Borie, C.; Ackermann, L.; Nechab, M. Chemical Society Reviews 2016, 45 (5), 1368-1386.
    Résumé : The indanyl core is ubiquitous in a large variety of drugs and natural products. Importantly, the ever-increasing demand for chiral catalysts bearing this scaffold calls for state of the art methods allowing for a step-economical enantioselective access to this structural motif. We herein summarize the asymmetric syntheses of indanes with a particular focus on asymmetric catalysis, covering the literature of the last decade until July 2015.
    Mots-clés : beta-keto-esters, bond-forming reactions, chiral 3-substituted indanones, conjugate addition, hypervalent iodine reagents, insertion reactions, kinetic asymmetric transformations, one-pot synthesis, quaternary stereocenters, reductive-heck reaction.

  • Borie, C.; Vanthuyne, N.; Bertrand, M. P.; Siri, D.; Nechab, M. Acs Catalysis 2016, 6 (3), 1559-1564.
    Résumé : The conversion of propargylic carbonates into allenes via Pd-catalyzed coupling with arylboronic acids, followed by tandem intramolecular Alder-ene cyclization, proceeds with remote diastereocontrol in the formation of indenes possessing two stereogenic elements (stereocenter and chiral axis). Highly configurationally stable atropisomers have been obtained with dr values up to >98:2. The reaction tolerates a range of commercially available functionalized arylboronic acids and allows the creation of C(sp(2))-C(sp(2)) and C(sp(2))-C(sp(3)) bonds in a single operation. Control experiments suggest that synergetic thermal and Pd-catalyzed cyclizations are likely to be involved in the second elementary step.
    Mots-clés : Alder-ene, alder-ene reaction, allenes, atropisomers, bond formation, boronic acids, cascade, cascade rearrangements, coupling reaction, Cyclization, enantioselective synthesis, ene-allenes, indenes, organic-synthesis, oxidative carbocyclization, palladium catalysis, propargylic alcohols, remote diastereocontrol.

  • Arif, T.; Borie, C.; Tintaru, A.; Naubron, J. - V.; Vanthuyne, N.; Bertrand, M. P.; Nechab, M. Advanced Synthesis & Catalysis 2015, 357 (16-17), 3611-3616.
    Résumé : Organocopper reagents react with readily available chiral conjugated diene-ynes to give indene derivatives bearing two stereogenic centres. The investigation of this original reaction in optically pure series demonstrates that a double transfer of chirality is operating. A stereocontrolled cascade involving S(N)2' followed by carbocupration and conjugate addition reactions accounts for the total recovery of the initial chirality. The scope and limitations of the reaction were investigated. The high diastereofacial discrimination in the cyclisation step allowed the construction of the quaternary stereocentre with excellent dr and ee, with the opposite configuration depending on the E- or Z-configuration of the alkene in the starting material. Post-functionalisation of indenes allowed the synthesis of indanyl derivatives containing four contiguous stereocentres.

  • Campolo, D.; Arif, T.; Borie, C.; Mouysset, D.; Vanthuyne, N.; Naubron, J. - V.; Bertrand, M. P.; Nechab, M. Angewandte Chemie-International Edition 2014, 53 (12), 3227-3231.
    Résumé : An original synthesis of chiral benzofulvenes triggered by organocopper reagents is reported. These enantiopure products are available through a highly chemo-, regio-, diastereo-, and enantioselective bis(alkylating) cycloisomerization process. A double chirality transfer (central-to-axial-to-central) is observed.

  • Gaudel-Siri, A.; Campolo, D.; Mondal, S.; Nechab, M.; Siri, D.; Bertrand, M. P. Journal of Organic Chemistry 2014, 79 (19), 9086-9093.
    Résumé : This article reports a theoretical study to explain how the intrinsic property of chirality is retained throughout the radical cascade rearrangement of an enantiopure chiral enyne-allene (bearing one stereogenic center) selected as a model for this family of reactions. Calculations at the MRPT2/6-31G(d)//CASSCF(10,10)/6-31G(d) level of theory were used to determine the entire reaction pathway which includes singlet state diradicals and closed-shell species. The cascade process involves three elementary steps, i.e., by chronological order: Myers-Saito cycloaromatization (M-S), intramolecular hydrogen atom transfer (HAT), and recombination of the resulting biradical. The enantiospecificity of the reaction results from a double transmission of the stereochemical information, from the original center to an axis and eventually from this axis to the final center. The first two steps lead to a transient diradical intermediate which retains the chirality via the conversion of the original static chirogenic element into a dynamic one, i.e., a center into an axis. The only available routes to the final closed-shell tetracyclic product imply rotations around two sigma bonds (sigma(C-C) and sigma(C-N), bonds beta and alpha respectively). The theoretical calculations confirmed that the formation of the enantiomerically pure product proceeds via the nonracemizing rotation around the sigma(C-C) pivot. They ruled out any rotation around the second sigma(C-N) pivot. The high level of configurational memory in this rearrangement relies on the steric impediment to the rotation around the C-N bond in the chiral native conformation of the diradical intermediate produced from tandem M-S/1,5-HAT.

  • Campolo, D.; Gastaldi, S.; Roussel, C.; Bertrand, M. P.; Nechab, M. Chemical Society Reviews 2013, 42 (21), 8434-8466.
    Résumé : Substrates, bearing axial chirality, can cyclize intra-or inter-molecularly with concomitant transfer of axial-to-central chirality to produce at least one stereocenter. In order to satisfy a strict definition of axial-to-central chirality transfer, the initial axial chirality must be lost during the cyclization process. Highly functionalized enantiopure carbocycles and heterocycles were prepared using this strategy. The transformations of configurationally stable substrates take place with high regio- and stereo-selectivity. Selected examples involving allenes, biaryls, arylamides and transient axially chiral short-lived species are discussed. Special attention is focused on the mechanistic rationale of the chirality transfer.

  • Mondal, S.; Bertrand, M. P.; Nechab, M. Angewandte Chemie-International Edition 2013, 52 (3), 809-811.

  • Mondal, S.; Dumur, F.; Barbarat, B.; Grauby, O.; Gigmes, D.; Olive, D.; Bertrand, M. P.; Nechab, M. Colloids and Surfaces B: Biointerfaces 2013, 112, 513-520.
    Résumé : Two novel enediynes containing an aromatic ring and substituted by two thiol functions as end-groups were designed and studied as functionalizing agent of gold nanoparticles. Phototriggered cyclization of the capping agent under UV–visible irradiation was investigated. Interestingly, the length of the thiol-substituted chain was shown to influence significantly the cyclization rate. Depending on the length of the spacer, either polymerization or simple cyclization of the coating agent was evidenced. The present study underscores the possibility of finely controlling the fate of the coating agent (polymerization/cyclization). Nanocomposites were characterized by UV–visible absorption spectroscopy, dynamic light scattering (DLS) technique and transmission electron microscopy (TEM) measurements. Finally, the ability of the colloidal solutions to induce photoinitiated damages to PcDNA3 supercoiled DNA was evaluated. Interestingly, an increase as high as 50% of the DNA cleavage could be registered when adding enediynes-capped gold nanoparticles to solutions of enediynes. In particular, the enhancement of DNA scission was observed in both thermal and photochemical activation modes.
    Mots-clés : Cyclization, DNA, Enediyne, Gold nanoparticles, Photochemistry.

  • Mondal, S.; Naubron, J. - V.; Campolo, D.; Giorgi, M.; Bertrand, M. P.; Nechab, M. Chirality 2013, 25 (12), 832-839.
    Résumé : The absolute configurations (AC) of azaheterocylic compounds resulting from the cascade rearrangement of enediynes involving only light atoms were unambiguously assigned by the joint use of vibrational circular dichroism (VCD) and copper radiation single crystal X-ray diffraction (XRD). These AC determinations proved that the rearrangements of enediynes proceeded with memory of chirality and retention of configuration. Chirality 25:832-839, 2013. (c) 2013 Wiley Periodicals, Inc.

  • Tehfe, M. - A.; Mondal, S.; Nechab, M.; Dumur, F.; Bertrand, M. P.; Graff, B.; Gigmes, D.; Fouassier, J. - P.; Lalevee, J. Macromolecular Chemistry and Physics 2013, 214 (12), 1302-1308.
    Résumé : New thiols for efficient thiol-ene polymerization reactions are presented. They do not exhibit any unpleasant odor, are characterized by quite good light-absorption properties at > 300 nm, and generate thiyl radicals upon UV-light exposure. Due to these interesting properties and contrary to many previously reported methodologies, the present thiol-acrylate polymerizations can be efficiently carried out without the presence of any additional photoinitiator. The chemical mechanisms are investigated by steady-state photolysis and electron spion resonance (ESR) experiments. Important parameters can also be extracted from molecular orbital calculations.

  • Campolo, D.; Gaudel-Siri, A.; Mondal, S.; Siri, D.; Besson, E.; Vanthuyne, N.; Nechab, M.; Bertrand, M. P. Journal of Organic Chemistry 2012, 77 (6), 2773-2783.
    Résumé : Memory of chirality (MOC) and deuterium-labeling studies were used to demonstrate that the cascade rearrangement of enediyne-connected amino esters la and 1b evolved through. exclusive 1,5- or 1,6-hydrogen atom transfer, subsequent to 1,3-proton shift and Saito-Myers cyclization, depending on the structure of the staffing material. These results were independently confirmed by DFT theoretical calculations performed on model monoradicals. These calculations clearly demonstrate that in the alanine series, 1,5-hydrogen shift is kinetically favored over 1,6-hydrogen shift because of its greater exergonicity. In the valine series, the bulk of the substituent at the nitrogen atom has a major influence on the fate of the reaction. N-Tosylation increases the barrier to 1,5-hydrogen shift to the benefit of 1,6-hydrogen shift. The ready availability of 1,6- hydrogen atom tansfer was explored as a potential route for the enantioselective synthesis of naphthoazepines.

  • Mondal, S.; Nechab, M.; Campolo, D.; Vanthuyne, N.; Bertrand, M. P. Advanced Synthesis & Catalysis 2012, 354 (10), 1987-2000.
    Résumé : The copper-catalyzed reaction of enediynes with diazo esters leads to cyclic amino esters bearing two contiguous tetrasubstituted stereogenic centers through a one-pot, five-step cascade. Copper iodide catalyzes the formation of an intermediate 3-alkynoate and copper carbenoid promotes its reversible isomerization to the corresponding allenoate. The alkynoate-allenoate equilibrium is completely shifted to the right by the rapid consumption of the allenoate by MyersSaito cyclization. This is followed by 1,5-H atom transfer and recombination of the resulting biradical. Memory of chirality phenomenon explains the high enantioselectivity.

  • Mondal, S.; Nechab, M.; Vanthuyne, N.; Bertrand, M. P. Chemical Communications 2012, 48 (19), 2549-2551.
    Résumé : The tandem Crabbe homologation-radical rearrangement of terminal enediynes leads, in a one-pot procedure, to the enantioselective synthesis of six- and seven-membered ring alpha-aminoesters bearing a quaternary stereocenter based on the phenomenon of memory of chirality.

  • Nechab, M.; Vanthuyne, N. Organic Letters 2012, 14 (15), 3974-3977.
    Résumé : Enantiopure tetrasubstituted skipped diynes were readily synthesized from N-protected amino esters upon addition of lithium TMS-acetylide which was found to be desymmetrizing through one-pot selective TMS-cleavage. The deprotection of the TMS group was realized through a one-pot silicon atom attack by the liberated methoxide, which was diastereoselective due to a conformational favorable chelate.

  • Tehfe, M. - A.; Lalevée, J.; Telitel, S.; Contal, E.; Dumur, F.; Gigmes, D.; Bertin, D.; Nechab, M.; Graff, B.; Morlet-Savary, F.; Fouassier, J. - P. Macromolecules 2012, 45 (11), 4454-4460.
    Résumé : Different polyaromatic structures (truxene derivatives and tris(aza)pentacene) are presented as new metal-free organic photocatalysts (OPC) to promote free radical polymerization FRP and ring-opening polymerization (ROP) under halogen lamp, household LED bulb, and laser diode (405 nm). These OPCs exhibit interesting light absorption properties and lead, through an oxidative catalytic cycle, to the formation of radicals and ions that can initiate both free radical polymerization FRP and ring-opening polymerization ROP. Interestingly, excellent polymerization profiles are obtained even upon visible light exposure. Using these very soft irradiation conditions, acrylate/epoxide blends are also easily polymerized under air and lead to the formation of interpenetrated polymer networks IPN exhibiting no phase separation.

  • Nechab, M.; Besson, E.; Campolo, D.; Perfetti, P.; Vanthuyne, N.; Bloch, E.; Denoyel, R.; Bertrand, M. P. Chemical Communications 2011, 47 (18), 5286-5288.
    Résumé : Mesoporous silica grafted with a tertiary amine was used as a basic nanocatalyst to promote in confined medium the enantioselective cascade rearrangement of enediynes based on the phenomenon of memory of chirality; the multi-substrates recyclable catalytic reagent could easily be recovered by simple filtration, and reused without any decrease in activity even when changing the solvent.

  • Nechab, M.; Campolo, D.; Maury, J.; Perfetti, P.; Vanthuyne, N.; Siri, D.; Bertrand, M. P. Journal of the American Chemical Society 2010, 132 (42), 14742-14744.
    Résumé : The cascade rearrangement of chiral enediynes 1c-e, involving successively 1,3-proton shift, Saito-Myers cyclization, 1,5-hydrogen atom transfer, and intramolecular coupling of the resulting biradical, proceeded at 80 degrees C to form tri- and tetracyclic heterocycles possessing a quaternary stereogenic center with a very high level of memory of chirality.