Photoinduced Copper-Promoted Decarboxylative Trifluoromethylselenolation of Aromatic Carboxylic Acids with [Me₄N][SeCF₃]

Abstract

Visible-light-induced decarboxylative trifluoromethylselenolation of (hetero)­aromatic carboxylic acids with [Me4N]­[SeCF3], oxidant, and catalysts afforded a variety of (hetero)­aryl trifluoromethyl selenoethers in good yields. The reaction might involve a radical process, which generated (hetero)­aryl radicals from the stable (hetero)­aromatic carboxylic acids via oxidative decarboxylation with NFSI as the oxidant, [di-tBu-Mes-Acr-Ph]­[BF4] as the photocatalyst, and 1,1′-biphenyl as the cocatalyst. Both catalysts had a decisive influence on the reaction. The trifluoromethylselenolation was further promoted by the copper salts probably via Cu-mediated cross-coupling of the sensitive SeCF3 species with the in situ formed (hetero)­aryl radicals. Advantages of the method include visible light irradiation, mild reaction conditions at ambient temperature, good functional group tolerance, no pre-functionalization/activation of the starting carboxylic acids, and applicability to drug molecules. This protocol is promising and synthetically useful, which overcame the limitations of the known trifluoromethylselenolation methods and represented the first decarboxylative trifluoromethylselenolation of (hetero)­aromatic carboxylic acids.

Photocatalytic Perfluoroalkylation of Disulfides and Diselenides. Syntheses of Perfluoroalkyl Thio- and Seleno-ethers

“…Nevertheless, akin to the R F S- reagents, the procedures for synthesizing R F Se- reagents are not always direct or cost-effective. Indirect protocols (where the Se and R F moieties are joined from different scaffolds) for the synthesis of aryltrifluoromethyl seleno-ethers rely on prefunctionalized substrates. − …”

Photoinduced Trifluoromethylselenolation of Aryl Halides with [Me4N][SeCF3]

“…The recent studies on CF 3 Se-containing amino acids and their derivatives, CF 3 Se bioisosteres of Riluzole and Pretomanid, CF 3 Se derivatives of nonsteroidal anti-inflammatory drugs, and insecticidal phenylpyrazole derivatives bearing a SeCF 3 moiety have verified the trifluoromethylselenolated compounds with improved cytotoxicity or potency, which demonstrated the great potential of SeCF 3 functionality in life sciences . Consequently, much effort has been made in the construction of C–SeCF 3 bonds by developing different trifluoromethylselenolation reagents and methodologies. , Among the known SeCF 3 sources (e.g., MSeCF 3 (M = 1/2Hg, Cu, Ag, Me 4 N), [(bpy)­CuSeCF 3 ] 2 , ClSeCF 3 , and TsSeCF 3 ), tetramethylammonium trifluoromethylselenate ([Me 4 N]­[SeCF 3 ]) has been considered to be the more versatile reagent because it has obvious advantages, such as good thermal stability, nonvolatility, easy preparation and handling, no involvement of metals and ligands, and rich chemistry, which have contributed heavily to the preparation of diverse SeCF 3 -containing molecules. − Thanks to the nucleophilicity and easy oxidation of [Me 4 N]­[SeCF 3 ], a variety of transition-metal-catalyzed, transition-metal-free, oxidative, and/or photoredox trifluoromethylselenolation reactions have been developed. − Even so, the use of [Me 4 N]­[SeCF 3 ] salt in modern and ecofriendly trifluoromethylselenolations is still immature. In this content, the search for efficient and environmentally benign methods for the incorporation of the SeCF 3 group into extensive organic scaffolds with [Me 4 N]­[SeCF 3 ] has attracted increasing attention, which would undoubtedly benefit the facile synthesis and application of the SeCF 3 -containing molecules.…”

“…In accordance with the above results and previous literature, , a plausible reaction mechanism was suggested for the visible-light-initiated trifluoromethylselenolation of aryl halides with [Me 4 N]­[SeCF 3 ] under metal-free conditions (Scheme ). Initially, intermolecular interaction of aryl halide ( 1 or 4 ) with the – SeCF 3 anion forms an EDA complex ( I ), which is activated by light irradiation and undergoes an intracomplex single electron transfer process with cleavage of the Ar–X bond to yield an aryl radical ( 5 ) and a •SeCF 3 radical (the latter is possibly further homocoupled to form CF 3 SeSeCF 3 ) (path A).…”