Strategy for Conditional Orthogonal Sequential CuAAC Reactions Using a Protected Aromatic Ynamine.

A method for conditional control of orthogonal sequential Cu-catalyzed azide-alkyne cycloaddition (CuAAC) reactions is reported. The inherent reactivity of an aromatic ynamine is controlled by a silyl protecting group that allows the selective CuAAC reaction of less reactive alkynes. Alternatively, the same protected ynamine undergoes selective CuAAC reaction via silyl deprotection in situ to give the ynamine click products. This allows complete orthogonal control of dialkyne systems and provides a unifying strategy for chemoselective CuAAC ligations in multialkyne/azide systems.