Reversible C−F Bond Formation and the Au-Catalyzed Hydrofluorination of Alkynes

The gold(I) fluoride complex [(SIPr)AuF] [SIPr = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene] reacts reversibly with 3-hexyne to form a (β-fluorovinyl)gold(I) species. The more stable fluorovinyl complex trans-{(SIPr)Au[(Ph)CC(F)CH3]}, formed by addition of [(SIPr)AuF] across 1-phenyl-1-propyne, has been characterized crystallographically. Both the protonolysis of a (fluorovinyl)gold complex and the reaction of a cationic (alkyne)gold(I) complex with the mild HF source Et3N•3HF result in fluoroalkene formation. Electrophilic gold(I) complexes, supported by N-heterocyclic carbene ligands and generated in situ, catalyze the trans-hydrofluorination of internal alkynes at room temperature. This catalysis represents a new, selective, and potentially versatile method for the synthesis of fluoroalkenes.