Light-Mediated Cross-Coupling of Anomeric Trifluoroborates

01 April 2021, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Stereoselective reactions at the anomeric carbon constitute the cornerstone of preparative carbohydrate chemistry. Here, we report the synthesis of axial C1 trifluoroborates and stereoselective C-arylation and etherification reactions under photoredox conditions. These reactions are characterized by high anomeric selectivities for 2-deoxysugars and broad substrate scope (24 examples), including disaccharides and trifluoroborates with free hydroxyl groups. Computational studies show that high axial selectivities for these reactions originate from a combination of kinetic anomeric effect of the intermediate C1 radical and stereoelectronic stabilization of Ni(III) through the metallo-anomeric effect. Taken together, this new class of carbohydrate reagents adds the palette of anomeric nucleophile reagents suitable for efficient installation C-C and Cheteroatom bonds.

Keywords

glycosylation
C-C cross-coupling
trifluoroborates
C-glycosides
photoredox catalysis

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