K₂S₂O₈‐Glucose‐Mediated Metal‐Free Oxidative Trifluoromethylation of Indoles with Langlois’ Reagent on the C2 Position

Abstract

An efficient and regioselective trifluoromethylation method of indole at the C2 position with ecologically-sound Langlois' reagent (CF 3 SO 2 Na) under metal-free conditions is described. K 2 S 2 O 8 in presence of glucose at room temperature has been utilized for the generation of CF 3 radicals from CF 3 SO 2 Na. The desired product can be obtained in good to excellent yields with a wide scope of substrate variability and gram scalability.

Photoinduced Synthesis of 2-Trifluoromethylated Indoles through Oxidative Trifluoromethylation Using Langlois’ Reagent in the Absence of External Photocatalyst

“…12,17 In a recent work by our group, we reported the synthesis of trifluoromethylated indoles with Langlois' reagent in the presence of persulfate and glucose at ambient temperature without any metal catalysts [Scheme 1(c)]. 18 The application of photocatalysis in preparative organic chemistry has opened avenues to achieve otherwise unviable chemical transformations. Photochemical strategies involving Langlois' reagent as the CF 3 radical source have been reported to require a strict anhydrous and oxygenfree environment along with the occasional use of transition metals.…”

Persulfate promoted regioselective C-1 thiocyanation of imidazo[1,5-a]pyridines under visible light irradiation in water

“…Recently, K 2 S 2 O 8 has been identified as a photoactive oxidising agent, which possesses the potential to initiate free radical organic transformation under visible light and mild reaction conditions. 20,21 In continuation of our interest in K 2 S 2 O 8 mediated radical chemistry [22][23][24] and photochemistry, 15,25 herein, we have reported a visible-lightinduced persulfate-promoted C-1 thiocyanation of imidazo [1,5-a]pyridines by using potassium thiocyanate under mild reaction conditions (Scheme 1f).…”

Kinetic Resolution of a Planar–Chiral [2.2]Paracyclophane via Michael Addition to Nitroolefins Catalyzed by N‐Terminal Guanidinylated Helical Peptide

“…[3][4][5][6][7] These endeavors have provided a wealth of important precursors for natural products and bioactive compounds. [8,9] In this regard, our group has recently reported the peptide-catalyzed asymmetric conjugate addition of β-dicarbonyl compounds to nitroolefins (Scheme 1a). [10] The catalytic ability originates from the incorporation of a strongly basic guanidinyl group attached to the N-terminal of the peptide chain, while a helical peptide with a (Leu-Leu-Aib) 3 unit provides the necessary chiral environment.…”