AlCl₃/Cyclohexane Mediated Electrophilic Activation of Isothiocyanates: An Efficient Synthesis of Thioamides

Abstract

An efficient protocol was developed for the Friedel Crafts type thioarylation for the synthesis of aromatic/heteroaromaticthioamide derivatives from aryl isothiocyanates and electron rich aromatic/heteroaromatic molecules by employing the Lewis acid AlCl3 and the less hazardous solvent cyclohexane at 70°C. The developed protocol offers advantages over the previous methods such as use of stoichiometric amount of reactants/reagent, less toxic solvent, shorter reaction time and higher yields.

From Carbodiimides to Carbon Dioxide: Quantification of the Electrophilic Reactivities of Heteroallenes

“…29 As expected from their low nucleophilicities, toluene (N = −4.36), furan (N = 1.33), and pyrrole (N = 4.63) do not undergo uncatalyzed reactions with 1c. 30 These arenes can be converted into the corresponding aromatic thioamides, however, by heating them with phenyl isothiocyanate (1c) in cyclohexane solution with stoichiometric amounts of AlCl 3 . 30 Diphenylcarbodiimide (1e, E = −20.14).…”

Recent Advances in AlCl3-Promoted Organic Reactions

“…并且硫代酰胺类化 合物在氮原子和硫原子处具有明显的亲核性 [54] , 可以 被用作合成具有重要意义的化合物骨架如苯并噻唑 [55] 等的起始原料. 2016 年, Nair 课题组 [56] 报道了以环己烷 为溶剂, 在 AlCl 3 促进下, 以芳基异硫氰酸酯和富电子 ( 异 ) 芳 香 族 化 合 物 为 原 料 , 进 行 傅 克 硫 酰 化 反 应 (Scheme 34 [58] .…”

Fe3O4@GlcA@Cu-MOF: A Magnetic Metal–Organic Framework as a Recoverable Catalyst for the Hydration of Nitriles and Reduction of Isothiocyanates, Isocyanates, and Isocyanides

“…13 Moreover, they can be used as flotation 14 and vulcanization agents, 15 as additives to lubricating oils and greases 16 and as interesting ligands in coordination chemistry. 17 Thioamides are often prepared via the reaction of isothiocyanates with aromatic compounds catalyzed by Lewis acids 18 (Scheme 2A), thioacylation of amines with thioformates, 19 dimethyl thioformamide, 20 or carbon mono 21 or disulfide 22 (Scheme 2B), formal oxygen−sulfur replacement on oxoamides in the presence of thionating agents including the Lawesson reagent, 23 phosphorus pentasulfide, 24 or elemental sulfur 25 (Scheme 2B), partial reduction of isothiocyanates with reducing agents (Scheme 2C), 26 and Schwartz reagent (Scheme 2,D). 27 Although useful, some of these methods suffer from one or more of the following drawbacks: the use of toxic reagents, unpleasant smelling, unstable reagents, harsh reaction conditions, tedious workup, and difficulty in separation and recovery of the catalyst.…”