21 research outputs found
Non-stabilized nucleophiles in Cu-catalysed dynamic kinetic asymmetric allylic alkylation
Frequency of Intrusions and Appraisal of Related Distress After Analogue Trauma: A Comparative Ecological Momentary Assessment Methods Study
Immunohistochemical study of the membrane attack complex of complement in IgA nephropathy
Synthesis, Application and Kinetic Studies of Chiral Phosphite-Oxazoline Palladium Complexes as Active and Selective Catalysts in Intermolecular Heck Reactions
International audienceThis study identifies new phosphiteâoxazoline ligands that have been successfully applied in the palladiumâcatalyzed intermolecular asymmetric Heck reaction. The design of the new phosphiteâoxazoline ligands derives from a previous successful generation of phosphineâoxazoline ligands, by replacing the phosphine group with several Ïâacceptor biaryl phosphite moieties. With these simple modifications, the new phosphiteâbased ligands, unlike previous phosphineâoxazoline, not only present a modular design with numerous potential phosphite groups available, but they are also airâstable solids, which can be made in the same number of synthetic steps as the phosphine analogues. The substitution of the phosphine by a biaryl phosphite group extended the range of substrates and triflates sources that can be coupled with regioâ, enantioselectivities and activities comparable to the few best ones reported. In addition, the ligands that provided the best selectivities contained an isopropyl oxazoline moiety instead of the tertâbutyl group found in the related phosphineâoxazoline ligands, which is made from a much more expensive precursor. In this paper we have also carried out kinetic studies and a Hammett plot analysis to determine the rate determining step of this system in the regime of interest. We suggest a likely explanation for the fast Heck reaction of the phosphiteâoxazoline catalysts