Mild, Efficient, and Metal-Free Radical 1,2-Dithiocyanation of Alkynes and Alkenes at Room Temperature

Abstract

A transition metal-free process has been reported for 1,2-dithiocyanation of alkynes in the presence of sodium persulfate and potassium thiocyanate reagent combination in a short reaction time under ambient air. Styrene derivatives are equally applicable under the same reaction conditions. Monothiocyanated vinyl derivatives were also synthesized from 2-ethynylpyridine and dimethyl acetylene dicarboxylate. The reaction proceeds by the radical/polar pathway as evidenced from our experiments and literature. After removal of the solvent from the reaction mixture by evaporation, the crude product was purified without conventional workup.

Construction of the 2-Amino-1,3-selenazole Skeleton via PhICl2/KSeCN-Mediated Selenocyanation/Cyclization

“…Interestingly, two distinctive NH peaks of the -NH 2 group emerged in the 1 H NMR spectrum, which indicated the formation of an intramolecular hydrogen bond, resulting in the deshielding of NH. The signal at δ 282.7 in the 79 Se NMR spectrum (Figure c, bottom) was identical to that of the selenium bonded to the CC group . All of those results combined with the characteristic signal at δ 75.0 in the 13 C NMR spectrum (Figure b, bottom) revealed the formation of selenocyanated enamino ester 2e′ at the beginning of this transformation.…”

“…The signal at δ 282.7 in the 79 Se NMR spectrum (Figure 2c, bottom) was identical to that of the selenium bonded to the CC group. 35 All of those results combined with the characteristic signal at δ 75.0 in the 13 C NMR spectrum (Figure 2b, bottom) revealed the formation of selenocyanated enamino ester 2e′ at the beginning of this transformation. Furthermore, 2e′ could be smoothly converted to the corresponding 1,3-selenazole 2e with the addition of K 2 CO 3 in EtOH (Scheme 2c).…”

Difunctionalization of Alkenes and Alkynes via Intermolecular Radical and Nucleophilic Additions

“…The research group also extended the scope of the reaction of aryl alkenes under photoredox conditions and using alkyl nitriles as nucleophiles to afford aminosulfonylation products 43 (Scheme 24B) [47]. Majee and coworkers reported a method for dithiocyanation of alkynes and alkene with KSCN and Na2S2O8 to give products 44 and 45, respectively (Scheme 25) [48]. In th reaction of alkynes, the thiocyanate radical generated from the oxidation of KSCN add to alkynes, followed by oxidization and reaction with KSCN to give dithiocyanation al kenes 44.…”

“…Majee and coworkers reported a method for dithiocyanation of alkynes and alkenes with KSCN and Na 2 S 2 O 8 to give products 44 and 45 , respectively ( Scheme 25 ) [ 48 ]. In the reaction of alkynes, the thiocyanate radical generated from the oxidation of KSCN adds to alkynes, followed by oxidization and reaction with KSCN to give dithiocyanation alkenes 44 .…”

Dithiocyanation of Alkynes with N‐Thiocyanato‐dibenzenesulfonimide and Ammonium Thiocyanate

“…In 2001, Moriarty disclosed the dithiocyanation of alkynes using in‐situ generated PhI(SCN) 2 with (dichloroiodo)benzene and Pb(SCN) 2 through an iodirenium ion intermediate (Scheme 1b) [5c] . In 2018, Xu and He, [6a] and Majee [6b] reported similar methodology of SCN⋅ radical addition reactions with MSCN (M=K, Na) and Oxone or sodium persulfate as the oxidant respectively (Scheme 1c). However, using heavy metals such as lead and excessive amount of oxidants sometime rise healthy and environmental concerns [7] .…”