One‐Pot Thioetherification of Aryl Halides Using Thiourea and Alkyl Bromides Catalyzed by Copper(I) Iodide Free from Foul‐Smelling Thiols in Wet Polyethylene Glycol (PEG 200)

Abstract

In this article, we have developed a new protocol for the thioarylation of structurally diverse alkyl bromides such as benzyl, cinnamyl, n-octyl, cyclohexyl, cyclopentyl, and tert-butyl bromides with aryl iodides, bromides and an activated chloride using thiourea catalyzed by copper(I) iodide in wet polyethylene glycol (PEG 200) as an eco-friendly medium in the presence of potassium carbonate at 80 and 100 8C under an inert atmosphere. The process is free from foul-smelling thiols which makes this method more practical for the thioetherification of aryl halides. Another important feature of this method is the variety of alkyl bromides which are commercially available for the in situ generation of thiolate ions with respect to the existing protocols in which the less commercially available thiols are directly used for the preparation of arylthio ethers.

One‐Pot Copper‐Catalysed Thioetherification of Aryl Halides Using Alcohols and Lawesson's Reagent in Diglyme

“…through the in situ generation of S-alkylisothiouronium salts from the reaction of alkyl halides and thiourea, [8] were reported by Firouzabadi and coworkers. Subsequently, these odourless methods were developed using other sulfur surrogates [9] such as xanthogenate, [10] thioacetamide, [11] thiourea, [12] potassium thiocyanate, [13] thioacetate, [14] sodium hydrosulfide, [15] sodium sulfide, [16] elemental sulfur, [17] sulfonyl hydrazides, [18] Na 2 S 2 O 3 , [19] potassium 5-methyl-1,3,4-oxadiazole-2-thiolate, [20] aminothiourea, [21] sulfonyl hydrazide, [22] and phosphorothioic acids and related compounds.…”

4,4′-Azopyridine as an easily prepared and recyclable oxidant for synthesis of symmetrical disulfides from thiols or alkyl halides(tosylates)/thiourea

“…[55][56][57][58][59][60][61][62] Another commonly used method of disulfide formation involves the reaction of alkyl halides with sulfur transfer reagents in the presence of an oxidant. [63][64][65][66][67][68][69][70][71][72][73][74] The reaction was claimed to be the oxidation of in situ-generated thiols which are formed from alkyl halides and the sulfur transfer reagent. This strategy decreases often encountered problems such as unpleasant odor of thiols and tedious work-up that is confronted when using methods involving direct oxidation of thiols.…”

Ligand-Free Copper-Catalyzed Synthesis of Diaryl Thioethers from Aryl Halides and Thioacetamide

“…In our case, a possible mechanism 8,13 for the present catalytic reaction was proposed in Scheme 2. First, the coupling of iodobenzene with thioacetamide affords phenyl ethanimidothioate (6) which is hydrolyzed in the reaction mixture to produce a thiol 7 under the basic conditions.…”