Chemoselective Layer-by-Layer Approach Utilizing Click Reactions with Ethynylcyclooctynes and Diazides

Ethynylcyclooctynes and diazides were synthesized and applied for a chemoselective sequence of copper(I)-catalyzed azide-alkyne cycloadditions and strain-promoted azide alkyne cycloadditions. Chemoselectivity within the reaction sequence was achieved by balancing three factors: Cu-catalysis/ring strain/steric shielding. A cholic acid derived triazide was subjected to the cycloaddition sequence as a model system for a layer-by-layer synthesis on surfaces.