Metal-Free and Redox-Neutral Conversion of Organotrifluoroborates into Radicals Enabled by Visible Light.

Converting organoboron compounds into the corresponding radicals has broad synthetic applications in organic chemistry. To achieve these transformations, various strong oxidants such as Mn(OAc)3 , AgNO3 /K2 S2 O8 , and Cu(OAc)2 , in stoichiometric amounts are required, proceeding by a single-electron transfer mechanism. Established herein is a distinct strategy for generating both aryl and alkyl radicals from organotrifluoroborates through an SH 2 process. This strategy is enabled by using water as the solvent, visible light as the energy input, and diacetyl as the promoter in the absence of any metal catalyst or redox reagent, thereby eliminating metal waste. To demonstrate its synthetic utility, an efficient acetylation to prepare valuable aryl (alkyl) methyl ketones is described and applications to construct C-C, C-I, C-Br, and C-S bonds are also feasible. Experimental evidence suggests that triplet diacetyl serves as the key intermediate in this process.