(768f) Photo-Mediated CuAAC Reaction: Capabilities and Applications

The, Copper Catalyzed Azide-Alkyne Cycloaddition reaction, CuAAC lends itself to become the standard of click chemistry due to its reliability, specificity and biocompatibility. The CuAAC reaction is catalyzed via copper (I) which has been generated using different approaches. The new approach we aimed to use is photo-mediated CuAAC.  Unlike conventional approaches using copper(I) salts, reducing agents, or copper turnings, a photo-mediated technique for generating copper(I) in situ affords comprehensive spatial and temporal control of the CuAAC reaction. The reduction of the Cu(II) in situ can be performed by the photoreduction of specific  Cu(II) complexes via ligand metal charge transfer, LMCT, or using a variety of radical generators like photoinitiators. The purpose of this study is to enhance the photo-mediated CuAAC’s performance relative to other CuAAC approaches, evaluate different radical generators and Cu (II) complexes, and implement the results of our study in photoplymerization reactions. The study found that the catalyst turnover is the rate limiting step, and the catalyst Cu(I) which is unstable is protected by ligands, so the reaction is not inhibited by oxygen. An addition, a 4-fold excess amount of ligands with respect to the concentration of the Cu(II) accelerates the reaction via a combination of cycle of redox-oxidation and increasing the charge in the metal by N-base ligands. The efficiency with which Cu(II)-complexes initiate the photo-mediated CuAAC reaction does not depend significantly on the quantum yield of the photochemistry process used to generate Cu(I). Other factors such as the nature of the ligand and the counter-ions do affect the reaction.

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Terminal alkyne

1,3 trizaole

Organic azide

Cu(I)