title: Enantiopure Sulfinyl Aniline as a Removable and Recyclable Chiral Auxiliary for Asymmetric C(sp3)-H Bond Activation.
abstract: An original and recyclable chiral bidentate aniline-sulfoxide-based directing group has been developed. This auxiliary allows challenging stereoselective Pd-catalyzed direct functionalization of small cycloalkanes through C-aryl and C-alkyl bond formation. Although moderate diastereoselectivities are observed, both optically pure enantiomers of the highly functionalized products can be obtained separately by simple silica gel chromatography and cleavage of the chiral auxiliary. This strategy was further applied to the preparation of enantiomerically pure 1,2,3-trisubstituted cyclopropane carboxylic acid derivatives, with three stereogenic centers and bearing both alkyl and aromatic substituents. These molecular scaffolds are not yet reported in the literature. The synthetic utility of this approach is validated by the chiral auxiliary being readily cleaved and recovered posteriori to the C-H activation step, without deterioration of its optical purity. Finally, an unprecedented palladacycle intermediate generated through C-H activation of the cyclopropane moiety has been isolated and fully characterized. Initial DFT calculations shed additional light on the reactivity of this original intermediate.
authors: Laboratoire de Chimie Moléculaire (UMR CNRS 7509), Université de Strasbourg, ECPM, 25 Rue Becquerel, 67087, Strasbourg, France.
authors: Soufyan
authors: S
authors: Jerhaoui
authors: Laboratoire de Chimie Moléculaire (UMR CNRS 7509), Université de Strasbourg, ECPM, 25 Rue Becquerel, 67087, Strasbourg, France.
authors: Faouzi
authors: F
authors: Chahdoura
authors: Laboratoire de Chimie Moléculaire (UMR CNRS 7509), Université de Strasbourg, ECPM, 25 Rue Becquerel, 67087, Strasbourg, France.
authors: Clémence
authors: C
authors: Rose
authors: LCSOM, Institut de Chimie de Strasbourg (UMR 7177), Université de Strasbourg, 4, rue Blaise Pascal, 67070, Strasbourg Cedex, France.
authors: Jean-Pierre
authors: JP
authors: Djukic
authors: Laboratoire de Chimie Moléculaire (UMR CNRS 7509), Université de Strasbourg, ECPM, 25 Rue Becquerel, 67087, Strasbourg, France.
authors: Joanna
authors: J
authors: Wencel-Delord
authors: Laboratoire de Chimie Moléculaire (UMR CNRS 7509), Université de Strasbourg, ECPM, 25 Rue Becquerel, 67087, Strasbourg, France.
authors: Françoise
authors: F
authors: Colobert
keywords: C−H activation; chiral auxiliaries; cyclopropane; sulfoxide