A Photocatalytic Approach to Radical 1-(Trifluoromethyl)cyclopropanation.

A simple protocol for the multigram-scale synthesis of 5-(1-(trifluoromethyl)cyclopropyl)dibenzothiophenium triflate is reported. This benchtop-stable reagent efficiently releases 1-(trifluoromethyl)cyclopropyl radicals under mild photochemical conditions, enabling the straightforward incorporation of that privileged chemotype at previously nonfunctionalized positions of (hetero)arenes and silyl enol ethers. The trifluoromethylcyclopropanation protocols herein reported are associated with an exceedingly broad substrate scope, remarkable functional group compatibility, high regioselectivity, and synthetically useful yields, making this reagent especially suitable for the preparation of medicinally relevant building blocks.