Copper-Catalyzed Intermolecular [4 + 2] Annulation Enabled by Internal Oxidant-Promoted C(sp)-H Functionalization: Access to 3-Trifluoromethylated 3-Hydroxy-cyclohexan-1-ones.

A copper-catalyzed diastereoselective [4 + 2] cyclolization of α,β-unsaturated ketoxime acetates and trifluoromethyl ketones affords various 3-trifluoromethylated 3-hydroxy-cylcohexan-1-ones smoothly. This reaction features the selective functionalization of a less acidic C(sp)-H bond by an internal oxdative C(sp)-H functionalization strategy. Preliminary investigations revealed that α,β-unsaturated ketoxime acetates were an internal oxidant, and the in situ generated HO served as the O-source of the carbonyl oxygen in the product.