A metal-free and a solvent-free synthesis of thio-amides and amides: an efficient Friedel–Crafts arylation of isothiocyanates and isocyanates

Abstract

A rapid, metal-free and solvent-free (very low-loading of solvent in few cases) reaction conditions for synthesizing thioamides and amides using the Bronsted super acid such as triflic acid has been developed. This method shows a broad substrate scope with a variety of electronrich arenes including thiophene derivatives. The reaction works well for both aromatic as well as aliphatic isothiocyantes. Most of the thioamides are obtained in excellent yields in short reaction duration of time and in most of the examples, a simple work up procedure has been developed which does not require further purification.

1,3‐Thiazolium‐4‐aminides: Syntheses and Characterization of Fluorescent Mesoionic Compounds

“…13 C NMR (100 MHz, CDCl 3 ): δ=124.4 (+, 2C), 124.8 (+, 1C), 127.2 (+, 1C), 128.1 (+, 1C), 129.2 (+, 2C), 133.2 (+, 1C), 138.6 (o, 1C), 148.1 (o, 1C), 188.0 (o, 1C) ppm. The data are in agreement with those reported in the literature [38] …”

“…in 30 mL of anhydrous toluene was stirred at reflux temperature for 4 h. After removal of the solvent in vacuo , the crude product was chromatographed (PE:EE, 5 : 1). Yield: 1.950 g (8.90 mmol, 98 %), green solid, mp 93–95 °C [38] . 1 H NMR (400 MHz, CDCl 3 ): δ=7.09 (dd, J H,H =5.1, 4.0 Hz, 1H), 7.27–7.31 (m, 1H), 7.39‐7.44 (m, 2H), 7.52 (bs, 1H), 7.54 (dd, J H,H =5.1, 1.0 Hz, 1H), 7.67 (d, J H,H =7.8 Hz, 2H), 8.98 (bs, 1H) ppm.…”

Friedel–Crafts-type reaction of pyrene with diethyl 1-(isothiocyanato)alkylphosphonates. Efficient synthesis of highly fluorescent diethyl 1-(pyrene-1-carboxamido)alkylphosphonates and 1-(pyrene-1-carboxamido)methylphosphonic acid

“…Friedel–Crafts-type reaction of arenes with isothiocyanates constitutes a useful method for the synthesis of aromatic secondary thioamides [ 1 – 6 ]. Our group [ 7 ] and others [ 8 ] have recently described an efficient modification of this method by using trifluoromethanesulfonic (triflic) acid as a promoter. Furthermore, we reported a simple procedure for the oxidative desulfurization of thioamides to amides via reaction with Oxone ® .…”

Synthesis of Isothiocyanates Using DMT/NMM/TsO− as a New Desulfurization Reagent

“…Natural as well as synthetic ITCs may additionally have anti-bacterial [ 27 , 28 , 29 , 30 ], anti-fungal [ 31 ], and anti-glioblastoma effects [ 32 ]. They are used in proteomics as probes [ 33 , 34 ], and in organic synthesis for the preparation of thioureas [ 35 ], thioamides [ 36 ], and heterocyclic compounds [ 37 , 38 ].…”