The Reactivity of α-Fluoroketones with PLP Dependent Enzymes: Transaminases as Hydrodefluorinases

A chemical method for the treatment of harmful halogenated compounds that has recently become of interest is the reductive dehalogenation of carbon–halogen bonds. In the case of a fluorine atom, this process is called hydrodefluorination. While many transition metal-based approaches now exist to reductively defluorinate aromatic fluoroarenes, the cleavage of C–F bonds in aliphatic compounds is not so well-developed. Here we propose a biocatalytic approach exploiting a promiscuous activity exhibited by transaminases (TAs). Hence, a series of α-fluoroketones have been defluorinated with excellent conversions using Chromobacterium violaceum and Arthrobacter sp. TAs under mild conditions and in aqueous medium, using a stoichiometric amount of an amine (e.g. 2-propylamine) as reagent and formally releasing its oxidized form (e.g. acetone), with ammonia and hydrogen fluoride as by-products. It is also demonstrated that this process can be performed in a regio- or stereoselective fashion.