A Highly Efficient Palladium-Catalyzed One-Pot Synthesis of Unsymmetrical Aryl Alkyl Thioethers under Mild Conditions in Water

Synthesis of Aryl Alkyl Thioethers via a Copper-Catalyzed Three-Component Reaction with DABSO, Aryldiazonium Salts, and Alkyl Bromides

We developed a method for synthesizing aryl alkyl thioether compounds via a three-component reaction involving aryldiazonium salts, 1,4-diazabicyclo[2.2.2]octane bis(sulfur dioxide), and alkyl bromides. Optimal yields were achieved when a copper catalyst was used in conjunction with zinc and tetrabutylammonium bromide in an acetonitrile solvent at 130 °C for 10 h. This methodology demonstrates good functional group tolerance and enables the successful synthesis of various aryl alkyl thioethers with moderate to high yields.

Improved, Odorless Access to Benzo[1,2-d;4,5-d']- bis[1,3]dithioles and Tert-butyl Arylsulfides via C-S Cross Coupling

Benzo[1,2-d;4,5-d′]bis[1,3]dithioles are important building blocks within a range of functional materials such as fluorescent dyes, conjugated polymers, and stable trityl radicals. Access to these is usually gained via tert-butyl aryl sulfides, the synthesis of which requires the use of highly malodorous tert-butyl thiol and relies on S_NAr-chemistry requiring harsh reaction conditions, while giving low yields. In the present work, S-tert-butyl isothiouronium bromide is successfully applied as an odorless surrogate for tert-butyl thiol. The C-S bond formation is carried out under palladium catalysis with the thiolate formed in situ resulting in high yields of tert-butyl aryl sulfides. The subsequent formation of benzo[1,2-d;4,5-d′]bis[1,3]dithioles is here achieved with scandium(III)triflate, a less harmful reagent than the usually used Lewis acids, e.g., boron trifluoride or tetrafluoroboric acid. This enables a convenient and environmentally more compliant access to high yields of benzo[1,2-d;4,5-d′]bis[1,3]dithioles.

Direct C-S bond formation via C-O bond activation of phenols in a crossover Pd/Cu dual-metal catalysis system

A dual-metal catalysis system including a newly prepared nanoparticle [SiO2@organic-linker(OL)@Pd(II)] and CuI was introduced with ultra-high catalytic activity (high turnover number (TON), up to 19 000) to a one-pot and odorless synthesis of unsymmetrical aryl sulfides by crossover C-S bond formation. The reaction proceeds via C-O bond activation of phenols and direct C-S bond formation in the presence of S8 as an oddorless sulfur source and aryl boronic acids under mild conditions (room temperature). The catalyst could be recycled up to five times without an obvious change in its activity.

Palladium-catalyzed direct arylation of indoles with arylsulfonyl hydrazides

A novel method to synthesise 2-arylindoles is demonstrated via direct arylation of indoles with arylsulfonyl hydrazides. Under the optimized reaction conditions, the reaction well tolerates a wide variety of functional groups to afford structurally diverse 2-arylindoles in good to excellent yields at 70 °C.

Microwave-Assisted, Metal- and Solvent-Free Synthesis of Diaryl Thioethers from Aryl Halides and Carbon Disulfide in the Presence of [DBUH]+[OAc]−

A microwave-assisted direct coupling between aryl halides and carbon disulfide in ionic liquid [DBUH]+[OAc]− (DBU = 1,8-diazabicyclo-[5.4.0] undec-7-ene) has been developed. The reactions are very efficient, affording the corresponding diaryl thioethers in moderate to high yields. Aryl chlorides could also be reacted with carbon disulfide using this protocol. Moreover, [DBUH]+[OAc]− could be easily recovered and reused for several runs.

The synthesis of symmetrical disulfides by reacting organic halides with Na2S2O3·5H2O in DMSO

Symmetrical disulfides were prepared by heating organic halides with Na₂S₂O₃ in DMSO in high yields and good purities.

Byproduct promoted regioselective sulfenylation of indoles with sulfinic acids

An unprecedented method to synthesise 3-sulfenylindoles is demonstrated via byproduct promoted sulfenylation of indoles with sulfinic acids in the absence of an external catalyst. The reaction selectively afforded structurally diverse indole thioethers in good to excellent yields in 1,2-dichloroethane at 80 °C.

An odorless, one-pot synthesis of nitroaryl thioethers via SNAr reactions through the in situ generation of S-alkylisothiouronium salts

The synthesis of nitroaryl thioethers using thiourea as the sulfur source in water by an odorless one-pot process was disclosed.

Efficient silver-catalyzed direct sulfenylation and selenylation of rich arenes

An efficient protocol for silver/copper-cocatalyzed direct sulfenylation and selenylation of arenes with aryl disulfides and diselenides has been developed.

Efficient Cu-catalyzed base-free C-S coupling under conventional and microwave heating. A simple access to S-heterocycles and sulfides

S-aryl thioacetates can be prepared by reaction of inexpensive potassium thioacetate with both electron-rich and electron-poor aryl iodides under a base-free copper/ligand catalytic system. CuI as copper source affords S-aryl thioacetates in good to excellent yields, by using 1,10-phenanthroline as a ligand in toluene at 100 °C after 24 h. Under microwave irradiation the time was drastically reduced to 2 h. Both procedures are simple and involve a low-cost catalytic system. This methodology was also applied to the “one-pot” synthesis of target heterocycles, such as 3H-benzo[c][1,2]dithiol-3-one and 2-methylbenzothiazole, alkyl aryl sulfides, diaryl disulfides and asymmetric diaryl sulfides in good yields.