Au(I) Catalyzed HF Transfer: Tandem Alkyne Hydrofluorination and Perfluoroarene Functionalisation

HF transfer reactions between organic substrates are an incredibly rare class of transformation. Such reactions require the development of new catalytic systems that can promote both defluorination and fluorination steps in a single reaction sequence. Herein, we report a novel catalytic protocol in which an equivalent of HF is generated from a perfluoroarene | nucleophile pair and transferred directly to an alkyne. The reaction is catalysed by [Au(IPr)NiPr2] (IPr = N,N’-1,3-Bis(2,6-diisopropylphenyl)imidazol-2-ylidene) and is 100 % atom efficient. HF transfer generates two useful products in the form of functionalised fluoroarenes and fluoroalkenes. Mechanistic studies (rate laws, KIEs, DFT calculations, competition experiments) are consistent with the Au(I) catalyst facilitating a catalytic network involving both concerted SNAr and hydrofluorination steps. The nature of the nucleophile impacts the turnover-limiting step. The cSNAr step is turnover-limiting for phenol-based nucleophiles while proteodeauration likely becomes turnover-limiting for aniline-based nucleophiles. The new approach removes the need for direct handling of HF reagents in hydrofluorination and offers new possibilities to manipulate the fluorine content of organic molecules through catalysis.