An NMR Study of Chiral Glucopyranosyl-Based N-Heterocyclic Carbene-Palladium(II)-Pyridine Complex

Abstract

A new air-stable and easy-to-handle 1-(2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl)-3-butyl-imidazol-2-ylidene] Pd(pyridine)Br2 (complex 2) was synthesized from the imidazolium halide salts 1-(2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl)-3-butyl-midazolium bromide (compound 1) by reaction with Pd(OAc)2 in pyridine. Complex 2 contains multiple chiral centers on the sugar ring. The molecular structures of complex 2 were determined with elemental analysis and liquid-state nuclear magnetic resonance (NMR) spectra. 1H and 13C chemical shifts of complex 2 were fully assigned. It was found that the effects of the carbon and proton chemical environment on the sugar ring is more obvious than that on the butyl chain after formation of N-heterocyclic carbene-palladium(II)-pyridine (NHCs-Pd(II)-Py)-metal bond in the presence of multiple weakly coordinated oxygen.

Keywords

• liquid-state nuclear magnetic resonance
• glucopyranosyl-based n-heterocyclic carbene-palladium(ii)-pyridine