Carbotrifluoromethylation of Allylic Alcohols via 1,2‐Aryl Migration Promoted by Visible‐Light‐Induced Photoredox Catalysis

Abstract

Visible-light-enabled photocatalytic carbotrifluoro-methylations of allylic alcohols and sodium triflinate were explored through 1,2-migration of an aryl group, affording an efficient method for synthesis of b-trifluoromethyl-a-substituted carbonyl compounds under mild reaction conditions. This catalyst system is well tolerant of various synthetically useful functional groups.

Promising reagents for difluoroalkylation

“…165 The ruthenium(II)-catalyzed para-and meta-selective C-H difluoroalkylation of aniline derivatives with BrCF 2 CO 2 Et was reported by the Liang group (Scheme 83). 166 Mechanistic investigation implied that the key factor of the para-selective difluoroacetylation derived from the cycloruthenation that occurred at N-H and C-H simultaneously. The electronic effects of carboxylate ligands along with a base determined the selectivity.…”

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

“…The visible-light-photocatalytic carbotrifluoromethylation of allylic alcohols with NaSO 2 CF 3 through 1,2-migrationo fa na ryl group has been investigated by Cai and co-workers, [89] affording b-trifluoromethyl-a-substituted carbonyl compoundsu nder mild reaction conditions. The CF 3 radical is generated from oxidation of NaSO 2 CF 3 by visible-light-excited 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) photocatalyst [E red 1/ 2 (*PC/PC À ) =+1.…”

“…These results supported that the reaction should follow ar adicalp athway.I nterestingly,w hen the reactionw as performed in the presence of an O 2 atmosphere under otherwise identicalr eactionc onditions, benzophenone was furnished in excellent isolated yield, but no migratory product was observed. With the above control experiments and others,the authors [89] proposed ar eaction mechanismthat is depicted in Scheme 45, in which they considered that the photoexcited catalyst 4CzIPN* (see Figure 3f or photocatalyst structure) oxidizes the CF 3 SO 2 Na to CF 3 radicals, generating the radicala nion of the photocatalyst. In turn, the CF 3 radicals, add to the terminal olefinic carbon of the allylic alcohol, producing intermediate A whichb y1 ,2-aryl migration via spiro [2,5] Chandu, Sureshkumar and co-workers [90] have accomplished the synthesis of allylic compounds with the CF 3 group with high yield and E/Z selectivityu sing visible-light photoredox catalysis and sodium triflinate as at rifluoromethylation source, startingf rom vinylcyclopropanes.…”

Frontiers in Radical Fluoromethylation by Visible‐Light Organic Photocatalysis

“…The catalysis was also applied to the oxidation of 1 a . The Cai group reported the intramolecular carbo‐trifluoromethylation of allylic alcohols 15 via radical 1,2‐aryl migration for the synthesis of β‐CF 3 ‐ketones 16 (Scheme ) …”