Organocatalytic [3+2] Cycloadditions: Toward Facile Synthesis of Sulfonyl-1,2,3-Triazolyl and Fully Substituted 1,2,3-Triazolyl Glycoconjugates

Abstract

A general strategy was developed for the synthesis of Sulfonyl-1,2,3-triazolyl glycoconjugates (5a–n) and fully decorated 1,2,3-triazolyl glycoconjugates (6a–w & 6 aa-6 ah) in the presence of catalytic amounts of organocatalyst. Ramachary-Bressy-Wang organocatalytic azide-ketone [3+2]-cycloaddition (OrgAKC) reaction of β-keto sulfones act as internal alkynes with glycosyl azides are reported for the synthesis of Sulfonyl-1,2,3-triazolyl glycoconjugates at 50 °C in good to excellent yields of products in the presence of catalytic amounts of pyrrolidine (10 mol %). In the similar way, Ramachary OrgAKC reaction of a variety of substituted phenyl ketones as internal alkynes with different glycosyl azides are reported for the synthesis of 1,2,3-triazolyl glycoconjugates at room temperature in good to excellent yields with high regioselectivity in the presence of catalytic amounts of DBU (10 mol %) using DMSO as solvent. The work mainly focuses on the application of this methodology to making glycoconjugates and establishes an alternative tool for the synthesis of fully decorated glyco-triazoles from the already known copper catalysed azide-alkyne [3+2] cycloaddition (CuAAC), RuAAC and IrAAC click reactions.