Sustainable and Site‐Selective C−H Sulfenylation of Aromatic Compounds with Thiol using Catalytic Graphene Oxide and NaI

Abstract

Graphene oxide (GO) in combination with NaI is used as the catalytic system for site‐selective C−H sulfenylation of 1H‐indole, 2‐naphthol, resorcinol and 2‐naphthylamines with thiols. The reaction is usually achieved in the presence of metal catalysts as well as under metal‐free conditions using iodine and a strong oxidizing agent. The present protocol avoids the use of any metal catalysts, strong oxidizing agents and the use of thiols instead of other sulfur‐based reagents making it atom‐economic and environmentally benign. Broader tolerance to functional groups has been tested and a plausible mechanism is proposed. The recovered GO can be recycled without significant loss in catalytic activity up to four runs.

Sulfenylation of Indoles Mediated by Iodine and Its Compounds

“…Generation of molecular iodine proceeds through the oxidation of iodide anion by NO 2 , formed from NaNO 2 under acidic conditions [29] . Potassium and sodium iodides were successfully applied as additives in VO(acac) 2 ‐ [30] and graphene oxide‐catalyzed [31] sulfenylation of indoles at the 3 d position.…”

Sulfenylation of Arenes with Ethyl Arylsulfinates in Water

“…42 The crude mixture was purified via column chromatography using ethyl acetate/PE (1:30) as the eluent to give the product as a red solid (65.4 1-((4-Fluorophenyl)thio)naphthalen-2-amine (3e). 19 The crude mixture was purified via column chromatography using ethyl acetate/PE (1:30) as the eluent to give the product as a red solid ( 1-((4-Bromophenyl)thio)naphthalen-2-amine (3g). 92 The crude mixture was purified via column chromatography using ethyl acetate/PE (1:30) as the eluent to give the product as a red solid (89.8 mg, 90%); mp 107.5−109.5 °C; 1 H NMR (400 MHz, DMSO-d 6 ): δ 8.00 (d, J = 8.3 Hz, 1H), 7.80 (d, J = 8.9 Hz, 1H), 7.73 (d, J = 7.5 Hz, 1H), 7.40 (td, J = 3.5, 1.5 Hz, 2H), 7.37 (d, J = 2.0 Hz, 1H), 7.23−7.17 (m, 2H), 6.92 (d, J = 2.0 Hz, 1H), 6.90 (d, J = 2.0 Hz, 1H), 6.07 (s, 2H); 13 1-((4-Nitrophenyl)thio)naphthalen-2-amine (3h).…”

“…The sulfide nucleus is a key constituent of many nature products and biological systems. − The arylsulfides have been widely used in the field of total synthesis, medicinal chemistry, and materials science because of their unique biological activities and physical properties. − Therefore, the development of efficient strategies for aryl sulfides has received considerable attention. , Most of them construct C–S bonds by employing transition metal-catalyzed cross-coupling of thiols and their derivatives with organic halides/organic boronic acid. − However, these methodologies generally suffer from a prefunctionalized starting material, harsh reaction conditions, and the formation of toxic waste. Recently, metal-free and transition metal-catalyzed direct C–H sulfenylation of arenes and various sulfur sources are particularly attractive because direct functionalization of C–H bonds for the synthesis of aryl sulfides can shorten the reaction steps and minimize the amount of waste formed. − However, most of the reported protocols were established by using an organic solvent as the reaction media. From the perspective of green chemistry, water as a safe, cheap, and environmentally friendly solvent has been used in organic reactions. − In 2016, Deng et al developed a copper-catalyzed three-component reaction of arenes, iodohydrocarbon, and sulfur powder for the synthesis of aryl sulfides in water (Scheme a).…”

Recent Advances in Transition Metal-Free Sulfenylation of Indoles

“…In 2016, Sinha and co-workers [16] coalesced biocatalyst and chemocatalyst for direct sulfenylation of indoles as well as hydroxyaryls with readily available thiophenols using BSA-O 2 as cooperative oxidant in aqueous medium. Subse-Scheme 4 Iodine-catalyzed sulfenylation of indoles with thiophenols quently, Basu group [17] disclosed the sulfenylation of indoles with thiols in the presence of catalytic grapheme oxide and NaI using DMSO as both solvent and oxidant, Iida group [18] presented a flavin-iodine system realizing the novel direct sulfenylation of indoles with thiols under O 2 condition (Scheme 5). The mechanism of all iodine-catalyzed sulfenylation of indoles with additional oxidants proposed by these groups is coincident and presented in Scheme 6.…”