Asymmetric Pd-catalyzed allylic substitution using a large sugar-based monophosphite ligand library. Scope and limitations.

Abstract

Asymmetric Pd-catalyzed allylic substitution using a large sugar-based monophosphite ligand library. Scope and limitations.Article en open accesWe have applied a modular sugar-based phosphite ligand library for the Pd-catalyzed allylic substitution reactions of several substrates. These ligands are derived from D-(+)-glucose, D-(+)-galactose and D-(+)-fructose, which lead to a wide range of sugar backbones, and contain several substituents at the C-3 carbon of the furanoside backbone and several substituents/configurations in the biaryl moiety, with different steric and electronic properties. Systematic variation of the ligand parameters indicates that the catalytic performance (activities and enantioselectivities) is highly affected by sugar backbone, the substituents at the C-3 carbon of the furanoside backbone, the configurations at the C-3 and C-4 carbons of the ligand backbone and the type of substituents/configurations in the biaryl phosphite moiety as well as the substrate type. For disubstituted substrates moderate enantioselectivities (up to 72%) were achieved using ligand L8d, while for monosubstituted substrates the highest enantioselectivities (up to 40%) were obtained using ligand L9a