Nouveaux ligands confinants dérivés de cyclodextrines. Applications en cycloisomérisation d’1,6-énynes catalysée a l’or

Abstract

This thesis is devoted to the synthesis and the characterization of new confining N-heterocyclic carbene (NHC) and P(III) ligands as well as to the study of their behavior in the gold-catalyzed cycloisomerization of 1,6-enynes. A new way of introducing an NHC bridging unit on a permethylated cyclodextrin platform has been developed. Benzimidazolium intermediates have been shown to be molecular receptors for anions compatible with the size of the cavity. Two regioisomeric NHC complexes of gold (I), of symmetry C1 and C2 respectively, were tested in several cycloisomerizations of 1,6-enynes, some being asymmetric, and allowed to obtain enantiomeric excesses of up to 50%. Among the phosphorus ligands used in this study, monodentate phosphoramidites derived from permethylated cyclodextrins constitute a new class of P(III) ligands capable of coordinating d10 metal cations such as gold(I) or silver (I). onto the surface of a cyclodextrin cavity. The performance of their gold(I) complexes in the cycloisomerization of 1,6-enynes was compared with that of other P(III) and NHC gold(I) complexes derived from cyclodextrins. The selectivities of the catalysts, in particular the enantioselectivity, have proved to be highly dependent on the ability of the ligands to position a substrate coordinated to the metal inside the cyclodextrin cavity