Triphenylbismuth Dichloride‐Mediated Conversion of Thioamides to Nitriles

Abstract

Thioamides were efficiently converted to nitriles using the pentavalent triphenylbismuth dichloride in combination with triethylamine. The reaction involved the dehydrosulfurization of primary thioamides to afford substituted aromatic or aliphatic nitriles in good to excellent yields. The process was also successfully extended to the synthesis of cyanamides starting from the corresponding thioureas and of thiocyanates from dithiocarbamates.

Synthesis of Tetracyclic Benzazole–Condensed Quinazolinones through Triphenylbismuth Dichloride Assisted Cyclodesulfurization

“…The reaction mechanism was considered to be similar to that of the Ph 3 BiCl 2 -mediated synthesis of N -substituted 2-aminobenzoxazoles from 2-aminophenols and isothiocyanates reported by us, 9 and the synthesis of nitriles from thioamides reported by Doris. 10 Thus, the possible mechanism for this cyclodesulfurization shown in Scheme 4 is based on the above control reactions and previous reports. Initially, the intermediate A is generated from the reaction of thioxoquinazolinone 3 and Ph 3 BiCl 2 ( 4a ) through sulfur atom attack of 3 on the bismuth center.…”

“…9 In addition, the second study from 2019 reported the dehydrosulfurization of thiomides and thioureas that yielded nitriles and cyanamides. 10 Moreover, the third study, published in 2022, involved the reaction of thioamides with benzimidoyl chloride, induced by the desulfurization and chlorination of thioamides and Ph 3 BiCl 2 , affording benzoxazoles. 11 Nevertheless, there are no reports on the one-pot tandem reaction of o -phenylenediamine derivatives and methyl 2-isothiocyanatobenzoate to synthesize benzazole-condensed quinazolinones using Ph 3 BiCl 2 as the cyclodesulfurization agent.…”

One-pot synthesis of 2-arylated and 2-alkylated benzoxazoles and benzimidazoles based on triphenylbismuth dichloride-promoted desulfurization of thioamides

“…In 2018, we reported the preparation of 2-aminobenzoxazoles by the Ph 3 BiCl 2 -mediated cyclodesulfurization of thioureas, which were obtained from 2-aminophenols and isothiocyanates [ 34 ]. In 2019, Doris et al performed the dehydrosulfurization of thioamides and thioureas that provided nitriles and cyanamides [ 35 ]. Using bismuth compounds as desulfurization reagents for synthesizing heteroazoles, this paper presents the syntheses of 2-aryl- and 2-alkylbenzoxazoles through the ring-closure reaction of 2-aminophenol with benzimidoyl chloride, which is produced by the desulfurization and chlorination of thioamides promoted by Ph 3 BiCl 2 without a base.…”

Synthesis of Nitriles <i>via</i> the Iodine-Mediated Dehydrosulfurization of Thioamides

“…The last of these examples is a particularly efficient approach, and involves the treatment of thioamides with diverse desulfurizing agents such as the transition metal reagents MnO 2 , 17) AgOAc, 18,19) Hg(OAc) 2 , 18) and Cu(OAc) 2 , 18) heavier main group reagents such as nBu 2 SnO, 20,21) diphosphorus tetraiodide, 22) telluroxide, 23) and tellurinic acid anhydride, 24,25) a combination of Zn(OTf) 2 13) or In(OTf) 3 26) with N-methyl-N-(trimethylsilyl) trifluoroacetamide, a combination of sulfur with sodium nitrite, 27) and other reagents such as benzotriazol-1-yloxytris(pyrrolidinol) phosphonium hexafluorophosphate, 28) 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 29) and formamide chlorides. 30) Moreover, an efficient method for the conversion of thioamides to nitriles using the organobismuth reagent, triphenylbismuth dichloride, 31) or gold nanoparticles 32) has been recently reported by Doris and colleagues, respectively. However, these reagents present disadvantages, such as high costs and toxicities, long reaction times or harsh reaction conditions.…”