Efficient coupling by oxygen accelerated photocatalyzed thiol-alkyne chemistry

Abstract

Thiol reactions have gained attention in many areas of chemical research, such as organic small molecule synthesis, polymer synthesis, and bimolecular coupling due to the “click” chemistry characteristics of this process. This work is a study of a novel method of photochemical thiol-alkyne reactions using alkyl halides and an Ir(ppy)3 photocatalyst. This process is shown to lead to rapid reactions and has the benefit of low catalyst and initiator concentrations relative to reagents. Remarkably, this reaction also has an unusual feature of an increased rate in the presence of oxygen, in contrast to many other types of radical processes. Catalyst and initiator concentrations and reaction conditions are varied in order to gain an understanding of the mechanism of this process. This chemistry is then applied to the synthesis of hyperbranched polymers and polymer networks to demonstrate potential applications.