37 research outputs found
ContrĂŽle de la chiralitĂ© axiale Ă lâaide dâarynes et en absence de mĂ©taux 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 accÚs 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 synthÚse 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 â 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 synthÚse 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
A concise atroposelective formal synthesis of (-)-steganone
The atroposelective formal synthesis of (-)-steganone, a parent member of Steganotaenia araliacea dibenzocyclooctadiene lignan lactones, was reported. The synthesis features an atropo-diastereoselective biaryl Suzuki-Miyaura cross-coupling with â€99% de using an enantiopure and efficiently converted ÎČ-hydroxy sulfoxide deriv. as chiral auxiliary
Oneâstep Oxidative Monofluorination of Electronâdeficient Sulfoxides to Access Highly Lewis Acidic Sulfur(VI) Cations
International audienc