Catalytic Formation of C(sp³)–F Bonds via Heterogeneous Photocatalysis

Abstract

Due to their chemical, physical and biological properties, fluorinated compounds are widely employed throughout society. Yet, despite their critical importance, current methods of introducing fluorine into compounds suffer from severe drawbacks. For example, several methods are non-catalytic, and employ stoichiometric equivalents of heavy metals. Existing catalytic methods, on the other hand, exhibit poor activity, generality, selectivity, and/or have not been achieved by heterogeneous catalysis, despite the many advantages such an approach would provide. Here we demonstrate how selective C(sp3)-F bond synthesis can be achieved via heterogeneous photocatalysis. Employing TiO2 as photocatalyst and Selectfluor® as mild fluorine donor, effective decarboxylative fluorination of a variety of carboxylic acids can be achieved in very short reaction times. In addition to displaying the highest turnover frequencies of any reported fluorination catalyst to date (up to 1050 h-1), TiO2 also demonstrates excellent levels of durability, and the system is catalytic in the number of photons required i.e. a photon efficiency greater than 1 is observed. These factors, coupled with the generality and mild nature of the reaction system, represent a breakthrough toward the sustainable synthesis of fluorinated compounds.