Photoinduced Hydrodifluoromethylation and Hydromethylation of Alkenes Enabled by Ligand-to-Iron Charge Transfer Mediated Decarboxylation

Directly utilizing abundant and inexpensive sources of aliphatic carboxylic acids is highly attractive for the synthesis of CF2H- and CH3-containing compounds. Herein, we report a versatile photoinduced iron-catalyzed platform for hydrodifluoromethylation and hydromethylation of alkenes without the need of additional stoichiometric oxidants. These two transformations are accomplished by a visible-light-induced ligand-to-iron charge transfer open-shell activation system by using industrial chemical difluoroacetic and acetic acids as precursors and postulated to operate via a difluoromethyl and methyl radical-mediated decarboxylation mechanism. Experimental results show that the strategy is also applicable to the difunctionalization of unactivated alkenes. Meanwhile, this strategy provides a viable route for the synthesis of pharmaceutically active molecules containing deuterated methyl units. The protocol exhibits several features, including mild reaction conditions, divergent radical precursors, operational simplicity and scalability, good chemo- and regioselectivity, scalability supported by continuous flow technology, and the ability to provide high-value building blocks for applications in one step.