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.