Visible‐Light‐Enabled Trifluoromethylative Pyridylation of Alkenes from Pyridines and Triflic Anhydride

Abstract

A general strategy for visible‐light‐enabled site‐selective trifluoromethylative pyridylation of unactivated alkenes has been developed using pyridines and triflic anhydride (Tf2O). Intriguingly, the N‐triflylpyridinium salts, generated in situ from pyridines and Tf2O, serve as effective modular bifunctional reagents to install both CF3 and pyridyl groups to various olefins while controlling C4‐selectivity in radical addition to the pyridine core. This synthetic route exhibited broad substrate scope under metal‐free and mild photocatalytic conditions, granting efficient access to valuable C4‐alkylated pyridines and quinolines without requiring prefunctionalization of the reaction site.

Copper and Zinc Copromoted Bromo(chloro)trifluoromethylation of Alkenes and Alkynes with Trifluoromethanesulfonic Anhydride

“…On the basis of the above results and previous reports, ,− ,, a plausible mechanism for this reaction is proposed in Scheme . Initially, the reaction of Tf 2 O and 2,2′-bipyridine generates the corresponding N -triflylpyridinium salt A .…”

“…In those reactions, the trifluoromethyl radical was formed by single electron transfer (SET) reduction of the in situ-generated N -triflylpyridinium salt with the excited-state photocatalyst . Very recently, Hong and co-workers described the introduction of both CF 3 and pyridyl groups into olefins using N -triflylpyridinium salts as modular bifunctional reagents under photocatalysis (Scheme c) . These works demonstrated that Tf 2 O is an attractive alternative trifluoromethyl radical reagent through a combination of pyridine activation and photoredox catalysis.…”

“…4 Very recently, Hong and coworkers described the introduction of both CF 3 and pyridyl groups into olefins using N-triflylpyridinium salts as modular bifunctional reagents under photocatalysis (Scheme 1c). 5 These works demonstrated that Tf 2 O is an attractive alternative trifluoromethyl radical reagent through a combination of pyridine activation and photoredox catalysis.…”

Recent Advances on the Halo- and Cyano-Trifluoromethylation of Alkenes and Alkynes

“…Very recently, Qing and co-workers reported the first copper/zinc-copromoted chloro- and bromo-trifluoromethylation of alkenes and alkynes using inexpensive and simple materials such as trifluoromethanesulfonic anhydride (CF 3 SO 2 ) 2 O (Tf 2 O) [ 29 , 40 ] as trifluoromethylating reagent [ 41 ]. Thus, the reaction of alkenes and alkynes with Tf 2 O in the presence of copper salts such as CuX 2 (X = Br, Cl), Zn powder and 2,2′-bipyridine provided the corresponding bromo- or chlorotrifluoromethylated products in good yields.…”

Visible‐Light‐Enabled Trifluoromethylative Pyridylation of Alkenes from Pyridines and Triflic Anhydride

“…Forschungsartikel products.T he structure of 3v was unambiguously confirmed by X-ray crystallographic analysis. [17] Notably,t he current method could be expanded to interesting examples of substrates containing privileged scaffolds,s uch as coumarin and flavone,a ffording the corresponding products 3z and 3aa.I ti sn oteworthy that this protocol can also be extended to the electron-rich alkene,N -vinyl phthalimide to yield the desired product 3ab.Inall cases,the reactions proceeded with C4-selectivity,and none of the C2-products were detected.…”