α-Fluorination of carbonyls with nucleophilic fluorine

Abstract

Given the unique properties of fluorine, and the ability of fluorination to change the properties of organic molecules, there is significant interest from medicinal chemists in innovative methodologies that enable the synthesis of new fluorinated motifs. State-of-the-art syntheses of α-fluorinated carbonyl compounds invariably rely on electrophilic fluorinating agents, which can be strongly oxidizing and difficult to handle. Here we show that reversing the polarity of the enolate partner to that of an enolonium enables nucleophilic fluorinating agents to be used for direct chemoselective α-C–H-fluorination of amides. Reduction of these products enables facile access to β-fluorinated amines and the value of this methodology is shown by the easy preparation of a number of fluorinated analogues of drugs and agrochemicals. A fluorinated analogue of citalopram, a marketed antidepressant drug, is presented as an example of the preserved biological activity after fluorination.