Contrôle de la chiralité axiale à l’aide d’arynes et en absence de métaux de transition

International audienceThe modular construction of enantioenriched biaryl derivatives is presented. This approach is based on (a) an almost quantitative access to polybrominated precursors via a transition metal-free aryl-aryl coupling, the ARYNE-coupling, (b) the regioselective introduction of a traceless chiral auxiliary (an enantiopure para-tolylsulfinyl group), (c) the chemoselective functionalization of this auxiliary and (d) subsequent regioselective functionalization of the remaining bromine atoms without any racemization during these steps. Next, the atropo-selective coupling of in situ generated arynes and aryllithiums bearing various chiral auxiliaries (tert-butylsulfoxide, para-tolylsulfoxide, tartrate-derived chiral diethers and oxazolines) is described and applied to the formal synthesis of (-)-steganacin. La construction modulaire de dérivés biaryliques énantioenrichis est présentée. Cette approche est basée sur (a) un accès quasi quantitatif aux précurseurs polybromés via un 2 couplage aryle-aryle sans métaux de transition, le couplage ARYNE, (b) l'introduction régiosélective d'un auxiliaire chiral (un groupe para-tolylsulfinyl énantiopur), (c) la fonctionnalisation chimiosélective de cet auxiliaire et (d) la fonctionnalisation régiosélective subséquente des atomes de brome restants sans racémisation au cours de ces étapes. Ensuite, le couplage atropo-sélectif à l'aide d'arynes générés in situ et d'aryllithiums portant divers auxiliaires chiraux (tert-butylsulfoxyde, para-tolylsulfoxide, diéthers dérivés du tartrate et des oxazolines chirales) est décrit et appliqué à la synthèse formelle de la (-)-stéganacine

Transition-Metal-Free Synthesis of a Known Intermediate in the Formal Synthesis of (-)-Steganacin

International audienceThe formal synthesis of both enantiomers of a natural axially chiral biaryl, steganacin is reported. The previously developed atropo-diastereoselective coupling of an aryne and an aryllithium (the 'ARYNE coupling') allows for this synthesis. In each step, the axial configuration of the biaryl could be maintained. The key intermediate of literature was accessed without using transition metals, demonstrating the interest of the ARYNE coupling as a complement or an alternative to transition metal-catalyzed couplings

Tri- and difluoromethoxylated N-based heterocycles − Synthesis and insecticidal activity of novel F3CO- and F2HCO-analogues of Imidacloprid and Thiacloprid

International audienc

Organocatalyse énantiosélective à l'aide de phosphines chirales (études méthodologiques et synthèse de catalyseurs à structure ferrocénique)

ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Lithium/Element Exchange as an Efficient Tool for Accessing Atropo-enriched Biaryls via Arynes

This account documents the development of transition metal-free, aryne-mediated aryl-aryl coupling, the 'ARYNE coupling', which began in 2001 in Lausanne. ortho,ortho'-Di-, tri- and even tetrasubstituted biphenyls have now become accessible on a multi-gram scale. The reaction is perfectly regioselective and the obtained polybromobiphenyls can be submitted to regioselective bromine/lithium interconversions. The access to enantiopure biphenyls is now possible using enantiopure sulfoxides as chiral auxiliaries, which allow for subsequent chemoselective sulfoxide/metal exchange on each atropo-diastereoisomer with configurational stability of the intermediate biaryllithiums. Direct atropo-diastereoselective ARYNE coupling has been reported more recently

One‐step Oxidative Monofluorination of Electron‐deficient Sulfoxides to Access Highly Lewis Acidic Sulfur(VI) Cations

International audienc

Recent advances in transition metal-catalyzed Csp(2)-monofluoro-, difluoro-, perfluoromethylation and trifluoromethylthiolation

In the last few years, transition metal-mediated reactions have joined the toolbox of chemists working in the field of fluorination for Life-Science oriented research. The successful execution of transition metal-catalyzed carbon–fluorine bond formation has become a landmark achievement in fluorine chemistry. This rapidly growing research field has been the subject of some excellent reviews. Our approach focuses exclusively on transition metal-catalyzed reactions that allow the introduction of –CFH2, –CF2H, –CnF2n+1 and –SCF3 groups onto sp² carbon atoms. Transformations are discussed according to the reaction-type and the metal employed. The review will not extend to conventional non-transition metal methods to these fluorinated groups