Iridium photocatalysts in the generation of ketyl radicals: umpolung approaches to the synthesis of propargylic alcohols

The efficient preparation of propargyl alcohols has long been a subject of interest in the field of organic synthesis, considering their widespread application in processes for the discovery and preparation of pharmaceuticals and the total synthesis of complex natural products. The shortcomings of traditional synthesis methodologies incentivize research on novel strategies in pursuit of straightforward approaches, milder reaction conditions, more efficient use of costly materials, and a higher degree of safety. The present document reports the findings of a thesis project that aimed to investigate, and experimentally test the robustness of, two unique photocatalytic approaches to the synthesis of propargyl alcohols. Both methods revolve around the formation of ketyl radicals via application of IrIII polypyridyl complexes as photoredox catalysts, and their subsequent coupling to alkynyl radical traps to yield propargyl alcohols as final products. Results linked to a wide scope of reaction conditions are provided, exploring the effect of the application of different solvent types, temperatures, reaction times, catalyst types, and reactants and auxiliary reagents; such an array of experimental results provides potentially valuable information for the upscale and transfer of the processes to a context of industrial synthesis. Further purpose of the document and the experimental work is to reaffirm the benefits of a photocatalytic approach to organic synthesis, as a gateway to low-energy-expense, mild-conditions approaches to traditional and novel organic syntheses alike.