One‐Pot Catalyst‐Free Direct Sulfenylation of 1‐Aryl Pyrazolones with Aryl Thiols at Room Temperature

Abstract

A novel strategy for N‐chlorosuccinimide mediated direct sulfenylation of 1‐aryl pyrazolones using aryl thiols has been developed at room temperature. The protocol was found to be simple, efficient and transition metal‐free to afford the target products in good to excellent yields without further purification. The prepared compounds were characterised by 1H NMR, 13C NMR and IR spectroscopy. The skeleton of one of the synthesized compounds has been well confirmed by X‐ray single crystal diffraction (XRD) analysis as well as ORTEP diagram.

C−H Functionalization Reactions of 1‐Aryl‐5‐pyrazolones

“…The authors proposed radical mechanism (Scheme 45) for this transforma- In 2017, Kamani and coworkers developed a more convenient and substrate-compatible method for the direct sulfenylation of 1-aryl pyrazolones 1 using the combination of aryl thiols 25 with N-chlorosuccinamide (NCS) 23 a at room temperature (Scheme 46). [38] The reaction was carried out in one pot which provided the corresponding sulfenyl products 26 with 76-87 % yields. The reaction tolerated a broad variation in both coupling partners, which was of great significance for the rapid formation of CÀ S bond at room temperature.…”

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“…Pyrazole and its derivatives represent one of the most active classes of compounds, which exhibit broad spectrum of pharmacological activities like antimicrobial [26], anticonvulsant [27], anticancer [28], analgesic [29], anti-inflammatory [30], antitubercular [31,32], cardiovascular [33] etc. Considering the importance of the pyrazole and thiol frameworks, together with our growing interest in sulfur-containing compounds synthesis, herein we wish to report a novel and single step reaction strategy for the construction of thiol-substituted pyrazoles C-H bond sulfenylation under transition metal free conditions (scheme 1) [34].…”