Aminothiolation of alkenes with azoles and Bunte salts

We have developed an intermolecular aminothiolation of simple olefins using Bunte salt as a thiolating agent. This protocol produces thiyl free radicals under PIDA oxidation conditions, eliminating the need for transition-metal catalysts. The method has a wide range of substrate applicability and is suitable for large-scale preparation and late-stage modification of drug molecules.

Synthesis of Aryl Thioalkynes Enabled by Electrophilic Sulfenylation of Alkynes and the Following Elimination

An unexpected deprotonative process of thiirenium ions is presented, which provides a new synthesis of aryl thioalkynes directly from terminal alkynes via the electrophilic activation of the carbon-carbon triple bonds. The conditions are well compatible with various functional-group-substituted aryl alkynes. The direct elimination from the thiirenium ion intermediate, or its tautomer, benzyl vinyl carbocation, is supported by control experiments and labeling reaction.

Direct methylthiolation of C-, S-, and P-nucleophiles with sodium S-methyl thiosulfate

A practical and efficient methylthiolation that employed the typical Bunte salt sodium S-methyl sulfothioate as the sulfur source was described. This reagent could react with a variety of compounds such as alkynes, 1,3-diketones, thiols, selenol and H-phosphine oxides, affording methylthiolated products in moderate to excellent yields. The advantages such as easy preparation, air- and moisture-stability and high tolerance of functional groups demonstrated the potential of this reagent to be widely applied in organic synthesis. Notably, the robustness of this reagent was demonstrated by the late-stage modification of drug molecules of erlotinib.

Ag-Cu copromoted direct C2-H bond thiolation of azoles with Bunte salts as sulfur sources

A direct C2-H thiolation of azoles with Bunte salts was achieved under the combined action of copper and silver salts. This protocol could furnish various substituted 2-thioazoles in moderate to good yields. This method has a broad substrate scope and shows good functional group tolerance.

Selective synthesis of α-organylthio esters and α-organylthio ketones from β-keto esters and sodium S-organyl sulfurothioates under basic conditions

We described herein a selective method to prepare α-organylthio esters and α-organylthio ketones by the reaction of β-keto esters with sodium S-benzyl sulfurothioate or sodium S-alkyl sulfurothioate (Bunte salts) under basic conditions in toluene as the solvent at 100 °C. When 4 equivalents of a base were used, a series of differently substituted α-thio esters were obtained with up to 90% yield. On the other hand, employing 2 equivalents of a base, α-thio ketones were achieved after 18 h under air. Furthermore, after a shorter reaction time, the isolation of keto-enol tautomers was possible, revealing them as significant intermediates for the mechanism elucidation.

An MeSeSO3Na reagent for oxidative aminoselenomethylation of maleimides

Herein, we describe the design and synthesis of an MeSeSO3Na reagent, which proved to be a versatile selenomethylation reagent for copper-catalyzed aminoselenomethylation of maleimides.

Synthetic developments on the preparation of sulfides from thiol-free reagents

This critical review covers the main thiolating reagents with respect to their characteristics and reactivities. In fact, they are complementary to each other and bring different thiolation strategies, avoiding the hazardous thiol derivatives.

Synthesis and Diversification of Macrocyclic Alkynediyl Sulfide Peptides

The synthesis of rare macrocyclic alkynediyl sulfides by a Cu-catalyzed C_sp -S cross-coupling is presented. The catalytic protocol (Cu(MeCN)₄ PF₆ /dtbbpy) promotes macrocyclization of peptides, dipeptides and tripeptides at ambient temperature (14 examples, 23→73 % yields) via thiols and bromoalkynes, and is chemoselective with regards to terminal alkynes. Importantly, the underexplored alkynediyl sulfide functionality incorporates a rigidifying structural element and opens new opportunities for diversification of macrocyclic frameworks through S oxidation, halide addition and azide-alkyne cycloaddition chemistries to integrate sulfones, halides or valuable fluorophores (7 examples, 37→92 % yields).

Ni nanoparticle-confined covalent organic polymer directed diaryl-selenides synthesis

The present work describes the preparation of a new covalent organic polymer (COP) and its application as a hetero support for diaryl selenides synthesis. A nitrogen rich COP (CGP) has been synthesized via SNAr reaction of cyanuric chloride with guanidinium hydrochloride. The successful confinement of COP with Ni nanoparticles through post-synthetic transformations (Ni@CGP) provides excellent catalytic activity for the transformation of aryl halides into diaryl selenides using elemental selenium powder. The synthetic transformations are well confirmed using various modern analytical and spectroscopic techniques which reveal high chemical and thermal durability. The N-rich framework of CGP fortifies the confinement of Ni NPs. Ni@CGP provides an efficient approach for diaryl selenides synthesis using a very cheap selenating reagent under water benign solvent conditions (DMSO : H2O) at room temperature with high reusability. Significantly, our work not only contributes the opportunity for developing economical and effective non-noble metal decorated COPs as heterogeneous catalysts, but also delivers an efficient approach to produce industrially important C-Se coupling products.

General Cu-Catalyzed Csp-S Coupling

Copper-catalyzed cross-coupling of thiols and bromoalkynes affords a mild, rapid, and selective C_sp-S coupling with broad scope, enabling the use of aryl-, alkyl-, and silyl-substituted alkynyl coupling partners (38 total examples, 50-99% yields). Importantly, the method enables the preparation of difficult-to-access bis-heteroatom-functionalized (S,S-, S,P-, and S,N-) alkynes.

A synthetic guide to alkynyl sulfides

The relative stability and predictable reactivity of alkynyl sulfides make them ideal synthons for the development of new transformations. Classic methods for forming alkynyl sulfides relied on dehydrohalogenation approaches. However more recent methods have focused on employing umpolung strategies, as well as nucleophilic and electrophilic thiol alkynylation. In addition, the recent syntheses of Csp-S bonds have trended towards exploiting catalysis and expanding the reaction scope of the methods. A survey of existing methods to form alkynyl sulfides is presented as well as an evaluation with regards to the scope of each method, to provide the reader with an overview of advantages and limitations of current technology.

Visible light induced 3-position-selective addition of arylpropiolic acids with ethers via C(sp3)-H functionalization

Although the 2-position-selective decarboxylative coupling or addition of arylpropiolic acids with cyclic ethers has been intensively investigated, selective functionalization of arylpropiolic acids at the 3-position is still a big challenge. Herein, an intriguing and mild method for visible light induced regioselective addition of arylpropiolic acids by attacking exclusively at the 3-position with cyclic/acyclic ethers was developed. A variety of 3,3-bis-substituted acrylic acids were successfully obtained in moderate to excellent yields. A plausible reaction mechanism involving an energy transfer induced radical addition in the presence of visible light and photocatalyst was proposed.

Recent developments in palladium-catalyzed C–S bond formation

This review summarized the recent developments in palladium-catalyzed C–S bond formation involving sulfenylation and sulfonylation reactions.

Promoting Effect of Crystal Water Leading to Catalyst-Free Synthesis of Heteroaryl Thioether from Heteroaryl Chloride, Sodium Thiosulfate Pentahydrate, and Alcohol

It is observed the crystal water in sodium thiosulfate pentahydrate (Na₂S₂O₃·5H₂O) can promote its multicomponent reaction with heteroaryl chlorides and alcohols, providing a facile, green, and specific synthesis of unsymmetrical heteroaryl thioethers via one-step formation of two C-S bonds under catalyst-, additive-, and solvent-free conditions. Mechanistic studies suggest that the crystal water in Na₂S₂O₃·5H₂O is crucial in generating the key thiol intermediates and byproduct NaHSO₄, which then catalyzes the dehydrative substitution of alcohols with thiols to afford thioethers.

Copper-catalyzed direct and odorless selenylation with a sodium selenite-based reagent

Use of a new odorless, shelf-stable, easy to handle, practical and scalable direct selenylation reagent, NaO₂SeR, has been disclosed.

One-pot synthesis of glycosyl phenylthiosulfonates from sulfinate, S and glycosyl bromides

Glycosyl phenylthiosulfonates are reagents which are valuable for the S-glycosylation decoration of organic compounds and proteins. Here, one-pot multiple-component synthesis of glycosyl phenylthiosulfonates from sulfinate, sulfur powder and glycosyl bromides is reported. The reactions afford glycosyl phenylthiosulfonates in good yields under mild conditions. Further application and exploration of glycosyl phenylthiosulfonates are still on underway in our group.

Bunte Salt CH2FSSO3Na: An Efficient and Odorless Reagent for Monofluoromethylthiolation

A practical and efficient monofluoromethylthiolation that employs the typical Bunte salt, sodium S-(fluoromethyl) sulfurothioate, as the sulfur source is described. This reagent reacts readily with a variety of aryl amines and aryl thiols. The high tolerance of functional groups demonstrates the potential of this reaction. In addition, this method is suitable for the late-stage monofluoromethylthiolation of complex bioactive molecules.

Transition-metal-free KI-catalyzed regioselective sulfenylation of 4-anilinocoumarins using Bunte salts

An efficient and eco-friendly protocol for the KI-catalyzed regioselective sulfenylation of 4-anilinocoumarins with Bunte salts was established under metal-free conditions.