Determining the Origin of Rate-Independent Chemoselectivity in CuAAC Reactions: An Alkyne-Specific Shift in Rate-Determining Step.

ABSTRACT

We report a kinetic and spectroscopic analysis of alkyne-dependent chemoselectivity in the copper-catalyzed azide-alkyne click (CuAAC) reaction. Studies of six alkyne subtypes reveal that the rate-determining step (RDS) of an aromatic ynamine class is shifted from acetylide formation to the azide ligation/migratory insertion event allowing chemoselectivity independent of overall rate.