The importance of CF3-containing molecules in pharma and agrochemicals motivates continued efforts to develop new methods for trifluoromethylation of unactivated C–H bonds. (Photo)redox methods to generate electrophilic ●CF3 are robust and powerful, but these outer-sphere methods suffer from the lack of selectivity inherent to ●CF3 radicals. Efforts to develop organometallic base metal catalysts for trifluoromethylation are challenged by the stability of M–CF3 bonds to low valent later 3d metals. We have elaborated a new photoinduced method to activate a thermodynamically stable Co(III)–CF3 bond for arene C–H trifluoromethylation. Co–CF3 activation occurs by a B12-like mechanism. Low energy visible light capture leads to intramolecular electron transfer from a redox-active [OCO] pincer ligand to Co, homolyzing the Co–CF3 linkage. The capacity of the Co(II) byproduct to catalyze H2 production permits direct arene C–H trifluoromethylation without a sacrificial or substrate-derived oxidant. This talk will present our recent efforts to extend this chemistry to intramolecular photolytic arene C–H trifluoromethylations where the (OCO)Co(CF3) core functions as both a chromophore and a scaffold to impart regiospecificity in C–H functionalization that occurs via ●CF3 transfer. Structure-property relationships will be discussed in the context of new ligand designs of selective radical alkylations. Extensions to catalysis will also be shown.

Regioselective radical trifluoromethylation via photoinduced Co–CF3 bond activation

2019 Spring National Meeting

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