Au@ZnO Core–Shell: Scalable Photocatalytic Trifluoromethylation Using CF₃CO₂Na as an Inexpensive Reagent under Visible Light Irradiation

Abstract

Trifluoromethylation is of significant importance for the synthesis of many small molecules vital for medicinal and agrochemical research. The importance of the CF3 group as well as the related synthetic challenges is so evident that many reagents have been reported for the synthesis of trifluoromethylated compounds, but these typical reagents are expensive and the methods for preparing them are difficult. Here, we report a new scalable and operationally simple trifluoromethylation reaction using sodium trifluoroacetate as a reagent and Au-modified ZnO as a photocatalyst under visible light irradiation. The reaction proceeds via trifluoromethylation of a broad range of aryl halides, arylboronic acids, and arene and heteroarene substrates. Some pharmaceutical and agrochemical compounds have been trifluoromethylated directly to demonstrate the applicability of the method.

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

“…Additiono ft riethanolamine and ammonium oxalate( hole (h +)s cavengers)g ave only trace of product. When radical scavenger TEMPO was added into the reactionm ixture, it formed the TEMPO-CF 3 adduct quantitativelyc onfirmed by 19 FNMR spectroscopy.B ased on the above and other control experiments, the authors [52] proposed ar eaction mechanism such as that depicted in Scheme 18.…”

“…Owing to localized surfacep las-mon resonance (LSPR), gold (Au) placed on semiconductorbased photocatalysts shows strong visible light absorption characteristics. [50,51] Bazyar and Hosseini-Sarvari [52] recently reported an ew simple trifluoromethylation reactionu sing CF 3 CO 2 Na as source of CF 3 radicals and Au-modified ZnO as ap hotocatalyst under visible light irradiation. The reaction can employ of ab road range of aryl halides, arylboronic acids, and arene and heteroarene substrates.…”

“…The authors [52] next studied the direct CÀHf unctionalization of activateda nd nonactivated (hetero)arenes with Au@ZnO core-shell nanoparticles as ap hotocatalyst and CF 3 CO 2 Na as a trifluoromethylation reagent. For aromatic homolytic substitutions, an externalo xidant was needed.…”

“…In this way,t he authors [53] show that carbonaceousp hotocatalysts possess favorable applicability in such chemical reactions. Althought he synthetic applicability of the protocol has not been widely explored by the authors, [53] an apparent advantage presented over the Au@ZnO [52] system,i st hat no external oxidant is employed to achieve HAS with the CF 3 moiety.…”

An Efficient Approach to 2-CF3-Indoles Based on ortho-Nitrobenzaldehydes

“…Most synthetic approaches to such indoles can be divided to the methods of direct trifluoromethylation of indole core and cyclizations of various precursors having CF 3 group in appropriate position [ 38 ]. Both radical and electrophilic trifluoromethylations was performed using bis(perfluoroalkanoyl) peroxides [ 48 ], difluorodiiodomethane [ 49 ], hypervalent iodine reagents [ 50 , 51 , 52 , 53 ], CF 3 I [ 54 , 55 , 56 , 57 , 58 ], Umemoto’s reagents [ 59 , 60 ], [(phen)CuCF 3 ] [ 61 ], and CF 3 SO 2 Na [ 62 , 63 , 64 , 65 ]. Cyclization approaches are based on formation of C2-C3 bond as a key step and deal with transformations of compounds having ortho -toluidine fragment [ 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 ].…”