Pierre-Yves Chavant

Asymmetric Strecker reactions of ketimines catalysed by titanium-based complexes

Abstract The asymmetric addition of TMSCN to a ketimine has been achieved by use of catalytic quantities of chiral titanium(IV) complexes. Fast conversions together with enantiomeric excesses as high as 59% have been achieved.

Organomanganese (II) reagents. XX: Manganese mediated barbier and reformatsky like reactions an efficient route to homoallylic alcohols and β-acetoxyesters

Abstract Allylic halides and α-bromoesters react with manganese metal in ethyl acetate; THF can also be used as solvent if a catalytic amount of zinc chloride is added to the reaction mixture. When the reaction is performed in the presence of various aldehydes or ketones, excellent yields of 1,2-addition products are obtained in preparative conditions.

Enhanced Spin-capturing Polymerization and Radical Coupling Mediated by Cyclic Nitrones

A series of cyclic nitrones have been tested for their spin-trapping activity in the enhanced spin-capturing polymerization of styrene and in nitrone-mediated radical coupling reactions. rac-2-Isopropyl-2,3-dimethyl-1-oxy-2,3-dihydro-imidazol-4-one was found to be the most efficient nitrone. The specific polystyrene macroradical addition rate to this nitrone was determined to be 8.0u2009×u2009103u2009Lu2009mol–1u2009s–1, which is by a factor of 10 higher than for previously studied compounds. Via enhanced spin-capturing polymerization, polymers in the range of oligomers to 30000u2009gu2009mol–1 were obtained. A strong dependence of molecular weight on monomer conversion was observed, which can be explained by the high trapping rate. In nitrone-mediated radical coupling, almost ideal coupling of bromine-functional polymers was obtained and the successful introduction of the residual alkoxyamine functionality confirmed.

New Reactions with Thioaldehydes and Thienium Cations

Abstract i) When generated under FVT conditions α-imino-thioaldehydes undergo a cyclization to dihydro-1,3-thiazoles. ii) Thienium cations, generated during a Pummerer reaction, can be trapped with dienes.