Metal-Free Visible-Light-Promoted Trifluoromethylation of Vinylcyclopropanes Using Pyrylium Salt as a Photoredox Catalyst

Abstract

Visible-light-induced metal-free trifluoromethylation of activated, carbocyclic, and unactivated vinylcyclopropanes via a ring-opening reaction using the Langlois reagent (CF 3 SO 2 Na) is reported to synthesize allylic trifluoromethylated derivatives. Allylic trifluoromethylation was achieved by a photo-oxidative single electron transfer (SET) process at an ambient temperature and under metalfree conditions and visible-light irradiation using pyrylium salt as a photoredox catalyst. The reported methodology has an operational simplicity, broad substrate scope, high functional group tolerance, and scalability.

Frontiers in Radical Fluoromethylation by Visible‐Light Organic Photocatalysis

“…CF 3 ‐alkanes 5 were obtained as products and related halo‐ and trifluoromethylthio‐trifluoromethylation were reported by Liu's group . In 2019, the Sureshkumar group reported the trifluoromethylation of vinylcyclopropanes 6 by T( p ‐CH 3 )PPT catalyst, leading to the production of CF 3 ‐allylic compounds 7 (Scheme b) . In all reactions, the key process is the generation of .…”

“…Particularly, Mes−Acr + ( N ‐Me‐9‐mesityl acridinium salt) and T( p ‐CH 3 )PPT (2,4,6‐tritolylpyrylium salt) have shown high oxidizing power in their excited states ( E * red =+2.06 and +1.8∼+2.3 V vs. SCE, respectively) . In 2013, Nicewicz et al.…”

“…[10] Particularly, MesÀ Acr + (N-Me-9-mesityl acridinium salt) and T(p-CH 3 )PPT (2,4,6-tritolylpyrylium salt) have shown high oxidizing power in their excited states (E* red = + 2.06 and + 1.8~+ 2.3 V vs. SCE, respectively). [7d, 11,12] In 2013, Nicewicz et al developed a hydro-trifluoromethylation method of alkenes 4 using the MesÀ Acr + catalyst (Scheme 3a). [11] CF 3 -alkanes 5 were obtained as products and related halo-and trifluoromethylthiotrifluoromethylation were reported by Liu's group.…”

“…[13] In 2019, the Sureshkumar group reported the trifluoromethylation of vinylcyclopropanes 6 by T(p-CH 3 )PPT catalyst, leading to the production of CF 3 -allylic compounds 7 (Scheme 3b). [12] In all reactions, the key process is the generation of * CF 3 from 1 a via direct oxidation by the photoexcited catalysts (*MesÀ Acr + and *T(p-CH 3 )PPT). Subsequently, the generated radical reacts with olefins to afford the radical intermediate A, followed by typical radical reactions including hydrogen atom transfer (HAT) and cyclopropylmethyl radical ring-opening.…”

New Visible‐Light‐Triggered Photocatalytic Trifluoromethylation Reactions of Carbon–Carbon Multiple Bonds and (Hetero)Aromatic Compounds

“…In the mechanism proposed by the authors, the Ir photocatalystsa cts in areductivequenching cycle. The same authors [91] have developed, in another report, as trategy for the trifluoromethylation of vinylcyclopropanes photocatalyzed by the metal-free pyrylium salt T(p-CH 3 )PPT (see Figure 3f or photocatalyst structure).…”