Metal- and Solvent-Free Ultrasonic Multicomponent Synthesis of (Z)-β-Iodo Vinylthiocyanates

Abstract

An eco-friendly and practical method for the ultrasonic multicomponent synthesis of diverse (Z)-β-iodo vinylthiocyanates from cheap and commercially available alkynes, molecular iodine, and KSCN through an intermolecular H-bonding assistance strategy was developed.

Potassium‐Persulfate‐Promoted Regioselective Azidation/Cyclization of 1,6‐Enynes

“…processes, whereas transition‐metal‐free transformations are underrepresented . However, transition‐metal‐mediated/catalyzed reactions are limited in application due to instinctive drawbacks of the catalytic systems . Therefore, the radical cascade cyclization of enynes under transition‐metal‐free conditions have received increasing attention from researchers recently.…”

Direct cyanation, hydrocyanation, dicyanation and cyanofunctionalization of alkynes

“…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). 42 In the plausible mechanism of the above ultrasonic multicomponent synthesis of (Z)-b-iodo vinylthiocyanates, an activated iodoirenium ion K 0 was formed through the molecular iodine electrophilic addition to alkyne with the release an iodine anion which was oxidized by (NH 4 ) 2 S 2 O 8 to regenerate I 2 for continuing participation in the reaction. Then, an energetically favourable six-membered ring intermediate L 0 was yielded by the coordination of HOAc to intermediate K 0 .…”

“…Finally, the thiocyanate anion attacked the less steric hindered carbon atom to give the corresponding product (Z)-b-iodo vinylthiocyanates with concomitant release of HOAc to complete the catalytic cycle (Scheme 32). 42 Synthesis of a variety of Z-b-thiocyanate alkenyl esters via lactic acid catalysed multicomponent hydrothiocyanation of alkynes was established (Scheme 33). Aer treating alkynes 59 with KSCN in the presence of natural lactic acid under ultrasound conditions for 30 min, the expected Z-b-thiocyanate alkenyl esters 60 was formed in excellent yields.…”

Selectfluor-initiated cyanation of disulfides to thiocyanates

“…Generally, thiocyanates can be synthesized via the following two major routes (Scheme 1(a)): (1) thiocyanation of organic partners (arenes, organic halides, diazonium salts, and arylboronic acids) in the presence of inorganic thiocyanates 10–15 and (2) cyanation of organosulfur compounds including thiols, disulfides, and sulfinates with electrophilic and nucleophilic cyanation reagents. 16–20 Thiocyanates can also be prepared via CuCN-mediated direct aerobic oxidative cyanation of thiophenols and diaryl disulfides. 21 While acknowledging the pioneering work in this field, the aforementioned methods still have some drawbacks.…”