Fe-Catalyzed Radical Trifluoromethylation and Cyclization of Ortho-Vinyl Enaminones with 1-(Trifluoromethyl)-1,3-benzo-[d][1,2]iodaoxol-3(1H)-one to Construct Functionalized Quinolines.

Abstract

Herein, we present a protocol for the construction of functionalized quinolines, i.e., 3-acyl-4-(2,2,2-trifluoro-ethyl)quinolines (ATFQLs) 4, from ortho-vinyl enaminones and 1-(trifluoromethyl)-1,3-benzo-[d][1,2]-iodaoxol-3(1H)-one, which was catalyzed by FeCp2 and promoted by FeCl3 (Lewis acid) additives in solvents (i.e., acetonitrile and toluene). This strategy first utilized the FeCp2-catalyzed functionalization of alkenes with trifluoromethyl radicals. The intermediate formed was captured by the ortho-iodobenzoate substrate, yielding intermediate 3, which then underwent the FeCl3-catalyzed elimination of ortho-iodobenzoate at a higher temperature to form an α,β-unsaturated intermediate. The subsequent intramolecular Michael reaction of the intermediate yielded the final target compound 4. In summary, a series of ATFQLs 4 were synthesized through the formation of two bonds (C═C and C-C).