Original Article:
Environmentally friendly synthesis of unsymmetrical dialkyl disulfides by reacting organic halides with thiourea and sodium thiosulfate in an aqueous medium
Xiaogang Lu, et al.
New J. Chem., 2019, 43, 16046-16049.
10.1039/C9NJ03024G
Owing to the widespread applications of sulfur-containing compounds in pharmaceutical, agricultural, and chemical fields, their synthesis has been continuously studied in the past few decades. Thiols are the most commonly used reagents for the synthesis of disulfides, but they are often associated with environmental toxicity and unpleasant odor. In recent years, increasing regulatory pressure on the manufacture and disposal of organic solvents has prompted the search for more environmentally friendly synthetic methods. It is worth mentioning that Bunte salts and thiourea have proven to be viable alternatives to thiols. Among them, Bunte salts can be conveniently synthesized from sodium thiosulfate (Na2S2O3).
Here, the researchers present a one-pot procedure involving the reaction of alkyl halides, thiourea, and a Bunte salt, in which the necessary thiols will be generated in situ, thus avoiding the direct use of thiols. Furthermore, this synthetic method is carried out in an aqueous medium, implying a reaction-friendly synthesis strategy for unsymmetrical dialkyl disulfides.
The proposed mechanism for the formation of asymmetric disulfides is shown in the figure. Concrete synthetic steps include:
> A Bunte salt intermediate R1S-SO3Na was synthesized from 4-chlorobutanenitrole and sodium thiosulfate by known methods.
> A variety of reaction conditions were screened in order to optimize the reaction between the Bunte salt, thiourea, and n-bromohexane as a model. These reaction conditions include solvents, catalysts, catalyst loading and temperature, etc.
Chemicals Related in the Paper:
| Catalog Number | Product Name | Structure | CAS Number | Price |
|---|---|---|---|---|
| ACM118526004 | Thiourea |  |
118526-00-4 | Price |
| ACM7772987 | Sodium thiosulfate |  |
7772-98-7 | Price |
