Dithiooxamide as an Effective Sulfur Surrogate for Odorless High‐Yielding Carbon–Sulfur Bond Formation in Wet PEG200 as an Eco‐Friendly, Safe, and Recoverable Solvent

Abstract

In this study, we have employed dithiooxamide, a solid, odorless, and commercially available compound, as a sulfur surrogate for the preparation of dialkyl sulfides from available alkyl halides in high yields. This sulfur transfer agent was also used for a copper‐catalyzed high‐yielding preparation of diaryl sulfides from their available aryl halides and for the preparation of thia‐Michael adducts in high yields. All the reactions were performed under odorless conditions in wet PEG200 (PEG = polyethylene glycol), which is an eco‐friendly, safe, and recoverable solvent. The protocols were easily applicable to large‐scale operation.

Thia‐Michael Addition: An Emerging Strategy in Organic Synthesis

“…conceived an in situ synthesis of S-alkylisothiouroniums alts and, thus, studied amulticomponent strategy for the synthesis of thia-Michael adducts from organic halides 57,e lectron-deficient al-kenes 1,a nd thiourea derivative 58 and 59 (Scheme 47). [87] Unlike the previous example, their reactionf ailed in water, even after 24 h. Therefore, the authors switched to other "green" solvents, such as ionic liquids, and optimal results were obtained in aN a 2 CO 3 /wet-PEG200 system. This method displayed wide substrate scope in terms of halides 57,a nd primary,s econdary,t ertiary,a llylic, and benzylic halidesw ere welltolerated, thereby affordingt he corresponding products (3)i n good yields.…”

“…Furthermore, S-alkylisothiouroniums alts have generated some impetus as nontoxic, cheap,r eadily available, and easyto-use substitutes for thiols. [86,87] These highly stable ando dorless non-thiolic precursors are generated from the reaction of organic halidesw ith thiourea. Pioneering studies on the S-alkylisothiouronium-salt-based thia-Michael addition reaction was reported by the Ge and Li group in 2007, in which they employed alkylthiols with various electron-deficient olefins 1 to deliver b-mercapto derivatives 3 (Scheme 45).…”

Sequential Ytterbium(III) Triflate Catalyzed One‐Pot Three‐Component Thia‐Michael Addition

“…Nevertheless, most of these methods have some disadvantage, such as the need of a multistep synthesis for the preparation of thiol equivalents from malodorous free thiols, long reaction times, the use of hazardous materials, and the scarcity and high cost of some catalysts. To resolve these issues, recent studies have developed sulfur surrogates, such as potassium thiocyanate, potassium thioacetate, thiourea, thioacetamide, dithiooxamide, carbon disulfide, and sodium thiosulfate, through the in situ generation of the sulfur atom during the reaction process. Importantly, some previously reported sulfur surrogates, such as thiourea, sodium thiosulfates, and dithiooxamide, have been employed along with alkyl halides and Michael acceptors in one‐pot thia‐Michael addition reactions (Scheme b).…”

Eco‐compatible three component strategies for C‐S bond formation in thioether and S‐aryl‐carbamodithioate compounds catalyzed by copper(II) nanoparticles supported on modified AlPO4

“…Thioethers and S‐aryl‐carbamodithioates are the important classes of compounds, which have been widely used as intermediates in the synthesis of numerous compounds having biological and therapeutic applications. So far, thioether compounds have been prepared using various coordinated metals via cross coupling reaction of thiols with aryl halids .…”

“…In this regard, it is necessary to eliminate the isolation step of the hazardous thiol intermediates by generation of them in situ. For this purpose, thiol intermediates can be obtained in situ by using sulfur‐containing reagents including thiourea, potassium thiocyanate, potassium ethyl xanthogenate, potassium thioacetate, thioacetamide, aminothiourea, sodium hydrosulfide, elemental Sulphur, dithiooxamide, and carbon disulphide . On the other hand, harmful solvents should be replaced by water as a green and inexpensive medium, which is known as a popular solvent in the literature.…”