Catalytic Dehydrosulfurization of Thioamides to Nitriles by Gold Nanoparticles Supported on Carbon Nanotubes

Abstract

A gold-carbon nanotube nanohybrid was shown to act as an efficient heterogeneous catalyst in the smooth and selective conversion of thioamides to the corresponding nitriles. The reaction was performed under mild conditions (room temperature, atmospheric pressure of oxygen) using only a gold loading of 0.35 mol %. Substituted aromatic or aliphatic nitriles were produced in very good to excellent yields and the catalyst could be easily recycled and reused over several consecutive cycles with no loss in dehydrosulfurization performances.

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

“…In contrast, the smooth progress of this reaction using I 2 indicates the superiority of this method. In addition, phenol derivative 1c gave a complex mixture when the dehydrosulfurizing agent was changed from I 2 to Ph 3 BiCl 2 , 31) suggesting the superiority of the described protocol. Furthermore, sterically hindered ortho-substituted thioamides reacted to give the corresponding nitriles 2j and 2k without any difficulty.…”

“…The electronic nature (electron-rich or electron poor) of the substituents in the p-position did not affect the outcome of the reaction. The dehydrosulfurization reaction of phenol 1c using Ph 3 BiCl 2 31) reported by Doris and colleagues gave a complex mixture. In contrast, the smooth progress of this reaction using I 2 indicates the superiority of this method.…”

“…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.…”

Continuous Flow Photocatalytic Hydrogen Production from Water Synergistically Activated by TiO2, Gold Nanoparticles, and Carbon Nanotubes

“…With these features in mind, and as part of our long-standing interest in the development of supramolecular catalysts for various applications [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ], including energy-related functions [ 22 , 23 , 24 , 25 , 26 , 27 ], we report here an efficient system for the photo-production of molecular hydrogen from water by associating TiO 2 with carbon nanotubes and gold nanoparticles, to bring together the “best of three worlds”. Furthermore, due to the entangled nature of the carbon nanotube network, the CNT-based catalytic system can be integrated into a packed-bed microfluidic photoreactor [ 28 ] for the continuous flow production of H 2 .…”