Photoinduced Trifluoromethylation of Arenes and Heteroarenes Catalyzed by High‐Valent Nickel Complexes

Abstract

We describe as eries of air-stable Ni III complexes supported by as imple,r obust naphthyridine-based ligand. Access to the high-valent oxidation state is enabled by the CF 3 ligands on the nickel, while the naphthyridine exhibits either am onodentate or bidentate coordination mode that depends on the oxidation state and sterics,a nd enables facile aerobic oxidation of Ni II to Ni III .These Ni III complexes act as efficient catalysts for photoinduced C(sp 2 )ÀHb ond trifluoromethylation reactions of (hetero)arenes using versatile synthetic protocols.T his blue LED light-mediated catalytic protocol proceeds via ar adical pathwaya nd demonstrates potential in the late-stage functionalization of drug analogs.

Review and Theoretical Analysis of Fluorinated Radicals in Direct CAr−H Functionalization of (Hetero)arenes

“…The Sanford group has reported the ability of Ni IV (CF 3 ) 3 to produce ⋅CF 3 radical under similar conditions, and exploited it in a nickel‐catalyzed radical trifluoromethylation strategy utilizing the Umemoto reagent 55 as a source of CF 3 group [212] . Notably, the Khusnutdinova group disclosed another related approach based on light‐mediated homolysis of Ni III (CF 3 ) 2 species ( A ) [213] …”

PNP‐Pincer Ligands Armed With Methyls: New Tools To Control Sterics and Non‐Innocence

“…We synthesized the iPr PNP CMe2 and tBu PNP CMe2 Ru complexes and compared them to their non methylated counterparts (Scheme 2). [13] …”

“…Based on the large reactivity difference imposed by the four methyl groups, we expected to see differences in alcohol dehydrogenation catalysis as well, However, we were surprised by observing a non‐intuitive trend in that the most sterically hindered tBu PNP CMe2 complex 2‐CMe 2 was the most active, with the other methylated complex iPr PNP CMe2 1‐CMe 2 giving the least turnover (Scheme 3). [13] …”

“…Interestingly, 2‐CH 2 exclusively gave a hydrogenated ligand backbone complex 11 as the major product, that could be clearly differentiated from the three other congeners by specific NMR chemical shifts and single‐crystal X‐ray diffraction, while the other complexes gave the acetates 12 a – c as the main products (Scheme 4). The acetates, which were not seen for 2‐CH 2 , were likely produced by the Guerbet process which produces water that is needed to form the acetate [13] …”