Publications 2016

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PUBLICATIONS

Chem. Eur. J. 2016, 22, 11239-11244

A Major Advance in the Synthesis of Fluoroalkyl Pyrazoles: Tuneable Regioselectivity and Broad Substitution Patterns

E. Schmitt, A. Panossian, J.-P. Vors, C. Funke, N. Lui, S. Pazenok, F. R. Leroux

A novel approach towards highly functionalized fluoroalkyl pyrazoles was developed by using fluoroalkyl amino reagents in combination with a variety of fluorinated ketimines. Tuneable introduction of fluoroalkyl groups in the 3‐ and 5‐positions was possible by using vinamidinium intermediates or the corresponding enamino ketones after hydrolysis. These high‐value building blocks can give rise to a large number of analogues for bioactivity screening and discovering new heterocyclic bioactive ingredients in various life science fields.

Eur. J. Org. Chem. 2016, 26, 4545-4553

When Chirality Meets “Buchwald‐Type” Phosphines: Synthesis and Evaluation in Frustrated Lewis Pair‐, Lewis Base‐ and Palladium‐Promoted Asymmetric Catalysis

M. J. Fer, J. Cinqualbre, J. Bortoluzzi, M. Chessé, F. R. Leroux, A. Panossian

We describe the synthesis of axially chiral “Buchwald ligand”‐like biphenylphosphines in highly enantioenriched form. These monodentate phosphines, biphenyl analogues of Hayashi's MOP ligands, were evaluated in phosphine‐promoted organocatalysis and in hydrosilylations catalyzed by palladium or by frustrated Lewis pairs. As expected, the title phosphines appeared best suited for transition metal catalysis where they provided higher asymmetric induction.

Org. Chem. Front. 2016, 3, 1392-1415

A new approach toward the synthesis of 2,4-bis(fluoroalkyl)-substituted quinoline derivatives using fluoroalkyl amino reagent chemistry

F. Aribi, E. Schmitt, A. Panossian, J.-P. Vors, S. Pazenok, F. R. Leroux

The present work describes the unprecedented use of Fluoroalkyl Amino Reagents (FARs) to afford 2,4-bis(fluoroalkyl)-substituted quinoline derivatives in two steps. In contrast to the Combes reaction, this approach allows for the synthesis of numerous quinoline derivatives bearing two identical or different fluoroalkyl substituents in the 2 and 4 positions, under mild reaction conditions, in good yields and with a very good regioselectivity. This reaction is easily scalable and suitable for an industrial process.

Chimia 2016, 70, 43-47

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

A. Panossian, F. R. Leroux

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 biphenyls can be submitted to regioselective halogen/lithium interconversions. The access to enantiopure biphenyls is possible using enantiopure sulfoxides as chiral auxiliaries, which allow for subsequent selective sulfoxide/metal exchange on each diastereoisomer with configurational stability of the intermediate biaryllithiums. Direct atropo-diastereoselective ARYNE coupling has been reported more recently.

Tetrahedron 2016, 72, 5208-5220

Atropo-diastereoselective coupling of aryllithiums and arynes — variations around the chiral auxiliary

D. Augros, B. Yalcouye, A. Berthelot-Bréhier, M. Chessé, S. Choppin, A. Panossian, F. R. Leroux

The atropo-selective coupling of in situ generated arynes and aryllithiums bearing various chiral auxiliaries ortho to lithium (tert-butylsulfoxide, para-tolylsulfoxide, tartrate-derived chiral diethers and oxazolines) is described. Chiral oxazolines showed the best results in terms of yields of coupling products. Different reaction parameters like the nature of the aryne precursor, the oxazoline, the alkyllithium base or the solvent revealed to be crucial for obtaining good yields and for diastereoselection.

Eur. J. Org. Chem. 2016, 4, 725-732

Access to Atropisomerically Enriched Biaryls by the Coupling of Aryllithiums with Arynes under Control by Homochiral Oxazolines

B. Yalcouye, A. Berthelot-Bréhier, D. Augros, A. Panossian, S. Choppin, M. Chessé, F. Colobert, F. R. Leroux

We report the preparation of axially stereoenriched biphenyls by the coupling of in situ generated aryllithiums and arynes using chiral oxazoline auxiliaries. The design of the aryne precursors, the choice of oxazoline and the reaction conditions were key to accessing the desired, highly substituted, atropisomerically enriched biarylic products. In one case, the two atropo‐diastereomers could be obtained in isomerically pure form by column chromatographic separation and their absolute configurations established by X‐ray crystallography. The stereoselectivity of the reaction seems to be governed by subtle parameters.

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