[Pd(N,N-chelate)(olefin)] Complexes Containing Chiral Nitrogen Chelates Based on Carbohydrates – Enantioselectivity of Olefin Coordination

Abstract

Chiral N,N-chelates of formula 6-Me-pyridine–2-CH=N–R (1) and R–N=CH–CH=N–R (2) (R = 6-deoxy-α-D-glucoside or 6-deoxy-α-D-mannoside residue) and their palladium(0) complexes [Pd(N,N-chelate)(olefin)] (I) were prepared. Symmetrical type 2 ligands induced higher enantioselectivity in the coordination of prochiral olefins. The ability of a type 1 chelate to promote a stereoselective process was also assessed, i.e. dimethylfumarate inserted into the Pd–Me bond formed upon methylation of a type I complex with 50% ee. Finally, a water-soluble Pd0 complex was also prepared by deprotecting the alcoholic functions on the sugar residue, and its molecular structure determined through X-ray diffractometry.