Visible‐Light‐Induced Trifluoromethylation of N‐Aryl Acrylamides: A Convenient and Effective Method To Synthesize CF₃‐Containing Oxindoles Bearing a Quaternary Carbon Center

Abstract

Trifluoromethylation/arylation: N-aryl acrylamides undergo visible-light-induced tandem trifluoromethylation/arylation in the presence of a ruthenium photocatalyst with Togni's reagent as the CF3 source. This reaction serves as a powerful and ecofriendly synthetic method for the preparation of a variety of CF3 -containing oxindoles bearing a quaternary carbon center.

Photocatalytic fluoroalkylation reactions of organic compounds

“…A variety of reagents, such as CF 3 I, 50,[55][56][57]59,62,66,67 silver trifluoroacetate, triflyl chloride (CF 3 SO 2 Cl), 49,64 the Langlois reagent, the Togni reagent, 51,53,54,60,65 the Umemoto reagent, 48,52,58,63,65 and the Shibata reagent, 61 can act as trifluoromethyl radical (•CF 3 The excited catalyst can reduce the R f X source (oxidative quenching pathway), regeneration of the catalyst follows by means of an electron donor or else, the photoexcited catalyst could be reduced by an electron donor to a one-electron reduced species that transfers an extra electron to the R f X source (reductive quenching pathway).…”

“…: [Ru(bpy) 3 ] 2+ and facIr(ppy) 3 (bpy = 2,2´-bipyridine and ppy = 2-phenylpyridinate), can induce both oxidative 48,49,51,54,58,60,[63][64][65] and reductive 50,[55][56][57]59,62 quenching cycles, owed to the positive driving forces for electron transfer to typical perfluoroalkyl halides. 7 The competition of the two pathways precludes the elucidation of the molecular parameters of the catalysis.…”

Olefin difunctionalizations via visible light photocatalysis

“…Later, an effective photocatalytic methodology for the synthesis of CF 3 -containing oxindoles bearing a quaternary carbon center was explored by the same group (Scheme 21). 34 The reaction is carried out with Togni's reagent and a vast scope of N-aryl acrylamides to perform the corresponding products in 51-92 yields. N-Aryl acrylamides with a variety of substituted groups, such as a-substituted, N-protected substitution, or aryl ring could be tolerated.…”

Iridium, Tris[2-(2-pyridinyl-κN)phenyl-κC]-, (OC-6-22)-iridium

“…27 The synthesis of CF 3 -containing oxindoles is also possible under photoredox catalysis. 28 Upon photoexcitation, Ir(ppy) 3 can reductively quench Togni's reagent and CF 3 • can add to the alkene of N-aryl acrylamides. Although Ir(ppy) 3 gave good yields, the scope of the reaction was investigated using [Ru(phen) 3 ]Cl 2 that gave slightly higher yields in the optimization (eq 15).…”