Ultrasound-promoted Brønsted acid ionic liquid-catalyzed hydrothiocyanation of activated alkynes under minimal solvent conditions

Abstract

A facile, practical and eco-friendly protocol for the synthesis of various Z-vinyl thiocyanates under minimal solvent conditions was developed.

C4‐Selective Synthesis of Vinyl Thiocyanates and Selenocyanates Through 3,4‐Dihalo‐2(5H)‐furanones

“…Thiocyanates have important biological activities and drug properties, such as antibacterial, anticancer, antiviral, etc Importantly, due to the presence of the active CN in SCN group, thiocyanate derivatives as versatile intermediates can be handily transformed to other significant compounds, such as trifluoromethyl sulfides, sulfonyl chlorides, thiols, thiocarbamates, sulfur‐containing heterocycles, disulfides, thioethers, etc. Hence, researchers around the world have made considerable efforts to develop efficient methods for the synthesis of thiocyanate derivatives, including aromatic and vinyl thiocyanate derivatives …”

Direct cyanation, hydrocyanation, dicyanation and cyanofunctionalization of alkynes

“…This reaction provided an eco-friendly and practical protocol for the synthesis of Z-vinyl thiocyanates, having some features including the abundance and accessibility of raw materials, the usage of recyclable and reusable catalysts, a wide substrate scope with good to high yields, ease of scale-up and high energy efficiency. 41 A plausible mechanism for the above hydrothiocyanation was proposed in Scheme 30. Firstly, a cationic intermediate G 0 was generated by protonation of the activated alkyne with BAIL-1.…”

“…Finally, the capture of a proton dissociated from water by ultrasonic radiation proceeded from the less hindered face of intermediate J 0 , trans to SCN, thus leading to product Z-vinyl thiocyanates. 41 Ultrasonic multicomponent synthesis of (Z)-b-iodo vinylthiocyanates via hydrothiocyanation of alkynes was also studied. When alkynes 57 was treated with KSCN and I 2 in the presence of K 2 S 2 O 8 as the oxidant in MeCN at room temperature, the corresponding (Z)-b-iodo vinylthiocyanates 58 was yielded in 82-94% yield with Z/E from 11 : 1 to 28 : 1 (Scheme 31).…”

Brönsted Acidic Ionic Liquids Catalysed Sequential Michael‐Like Addition of Indole with Chalcones via Claisen‐Schmidt Condensation

“…The uses of environmentally benign strategies were observed with ionic liquids, supercritical fluids, glycerine, microwave and ultrasound‐assisted conditions . Many organic reactions employed task‐specific ionic liquids as non‐volatile solvent/catalyst system because of viscous nature and also reduced their toxic effects in environment as reusable material . The literature search also displayed few reports involving N‐alkane sulfonic acid functionalized Brönsted acidic imidazolium/ammonium based ionic liquids as dual solvent‐catalyst system for the Claisen‐Schmidt condensation at 100–160 °C for varied reaction time (1.5 h to 9 h) under inert atmosphere .…”