An Efficient Catalytic Method for Regioselective Sulfenylation of Electron-Rich Aza-Aromatics at Room Temperature

Iodine/DMF-Mediated Regioselective Sulfenylation Using Arenediazonium Tosylates and Sodium Metabisulfite: An Easy Access to 3-Arylthioindoles

A practical C3 sulfenylation of indoles has been accomplished using arenediazonium tosylates and sodium metabisulfite, with a key role of iodine/DMF combination in the reaction. The method involves scarce use of sodium metabisulfite as a divalent sulfur source and offers an array of structurally diverse 3-arylthioindoles in high yields under operationally simple transition-metal-free and mild conditions.

Iodophor-catalyzed sulfenylation of indoles with sulfonyl hydrazides for the synthesis of 3-sulfenylindoles

An iodophor-catalyzed sulfenylation of indoles using sulfonyl hydrazides as sulfur source to synthesize 3-sulfenylindoles in aqueous phase has been achieved. Notably, iodophor as catalyst and solvent is inexpensive, commercially available and no innocuous to the environment. The method is also easy to operate. Moreover, the synthetic strategy features a wide range of substrates with excellent tolerance to diverse functional groups. A plausible mechanism for the iodophor-mediated 3-sulfenylation of indoles with sulfonyl hydrazides has been proposed. In addition, 3-(phenylthio)-1H-indole was obtained on a multi-gram scale.

A Method for the Synthesis of Thioindoles through Copper-Catalyzed C-S Bond Coupling Reaction

We herein report the copper-catalyzed C-S bond coupling reaction of indoles with N-thiosuccinimides, resulting in moderate to excellent yields of mono- and bis-sulfenylated compounds such as arylthioindoles, alkylthioindoles, selenylated indoles, and cysteine-substituted indoles. Thioarylation and thioglycosylation at the C2 position of indole alkaloids in the Radix Isatidis were achieved via structural modification. The first total syntheses of isatindigotindolosides III and IV have been successfully carried out. The electrophilic sulfenyl bromides generated in situ can play an important role in the catalytic cycle.

Convenient and Efficient Synthesis of Functionalized 2-Sulfenylindoles

A simple, efficient, and practical sulfenylation at the C2 position of N-tosylindoles under mild conditions was developed. The designed transformation is based on the reaction of N-tosylindoles with BuLi and S-alkyl, and S-aryl phosphorodithioates or thiotosylates to produce 2-sulfenylindoles in moderate to high yields. The presence of additional hydroxy, carboxy, or amino functionalities did not disturb the formation of products.

Review of the Syntheses and Activities of Some Sulfur-Containing Drugs

Background:

Sulfur-containing compounds represent an important class of chemical compounds due to their wide range of biological and pharmaceutical properties. Moreover, sulfur-containing compounds may be applied in other fields, such as biological, organic, and materials chemistry. Several studies on the activities of sulfur compounds have already proven their anti-inflammatory properties and use to treat diseases, such as Alzheimer’s, Parkinson’s, and HIV. Moreover, examples of sulfur-containing compounds include dapsone, quetiapine, penicillin, probucol, and nelfinavir, which are important drugs with known activities.

Objective:

This review will focus on the synthesis and application of some sulfur-containing compounds used to treat several diseases, as well as promising new drug candidates.

Results:

Due to the variety of compounds containing C-S bonds, we have reviewed the different synthetic routes used toward the synthesis of sulfur-containing drugs and other compounds.

Iodine-Catalyzed Synthesis of 3-Arylthioindoles Employing a 1-Aryltriazene/CS2 Combination as a New Sulfenylation Source

A practical approach for the regioselective synthesis of 3-arylthioindoles has been accomplished using a combination of 1-aryltriazene/CS₂ as a new sulfenylation source. The methodology employs molecular iodine as a catalyst and is compatible with a variety of structurally diverse reactants.

Ditocopheryl Sulfides and Disulfides: Synthesis and Antioxidant Profile

Symmetrical ditocopheryl disulfides (Toc)₂ S₂ and symmetrical and unsymmetrical ditocopheryl sulfides (Toc)₂ S were simply prepared under remarkably mild conditions with complete control of the regiochemistry by using δ-, γ-, and β-tocopheryl-N-thiophthalimides (Toc-NSPht) as common starting materials. The roles of sulfur atom(s), H-bond and aryl ring substitution pattern on the antioxidant profile of these new compounds, which were assembled by linking together two tocopheryl units, are also discussed.

Iodine mediated oxidative cross coupling of 2-aminopyridine and aromatic terminal alkyne: a practical route to imidazo[1,2-a]pyridine derivatives

A novel, transition-metal free route leading to imidazo[1,2-a]pyridine derivatives via iodine mediated oxidative coupling between 2-aminopyridine and aromatic terminal alkyne has been demonstrated. This newly developed method discloses an operationally simple way for the construction of imidazoheterocycles. Commercially available antiulcer drug zolimidine may readily be synthesized employing this method.

Cu-Catalysed Direct Bis-Thiolation of Benzoheterocycles with Arylsulfonyl Hydrazides

A series of bis-arylsulfenylated indoles (10), benzofurans (3), and benzothiophenes (3) and of monosulfenylated indoles (5), 12 of which are novel, were prepared in good yields via a Cu-catalysed direct sulfenylation of benzoheterocycles with arylsulfonyl hydrazides. Sulfonothioates are probably the major thiolated intermediates in this transformation.

N-Hydroxy sulfonamides as new sulfenylating agents for the functionalization of aromatic compounds

An unprecedented use of N-hydroxy sulfonamides as sulfenylating agents has been established. In the presence of catalytic amounts of iodine and N-hydroxysuccinimide, N-hydroxy sulfonamides participated in sulfenylation with indoles, 7-azaindole, N-methyl pyrrole, and 2-naphthol to afford structurally diverse thioethers in moderate to excellent yields with very high regioselectivity.

I2-Catalyzed sulfenylation of indoles and pyrroles using triethylammonium thiolates as sulfenylating agents

Readily available triethylammonium thiolates were proven to be new and eco-friendly sulfenylating agents for the efficient and practical construction of sulfenylated indoles and pyrroles (48 examples) with good to excellent yields under metal-free and microwave irradiation conditions. The combination of I₂ and DMSO enabled direct C-S bond formation, allowing easy and low-cost access to new functionalized C,S-tethered bisindoles and pyrrole-indole pairs with a wide diversity of substituents. The mechanism involving S-S and S-I bond-forming/breaking events was proposed.

Synthesis of N-alkyl-3-sulfonylindoles and N-alkyl-3-sulfanylindoles by cascade annulation of 2-alkynyl-N,N-dialkylanilines

Divergent synthesis of N-alkyl-3-sulfonylindoles and N-alkyl-3-sulfanylindoles from 2-alkynyl-N,N-dialkylanilines and sulfonyl hydrazides has been described.

A conjugate Lewis base-Brønsted acid catalyst for the sulfenylation of nitrogen containing heterocycles under mild conditions

A new Lewis base/Brønsted acid approach allows for the sulfenylation of N-heterocycles under exceedingly mild conditions.

Cu-Catalyzed first direct access towards 3-sulfenylindoles from aryl halides

The copper-catalyzed cross-coupling of indole derivatives with aryl halides in the presence of thiourea proceeds to give 3-sulfenylindoles in DMSO at 120 °C.

Catalytic Synthesis of 3-Thioindoles Using Bunte Salts as Sulfur Sources under Metal-Free Conditions

An efficient catalytic method for the synthesis of 3-thioindoles has been successfully developed, which uses odorless, stable, readily available crystalline Bunte salts as the sulfenylating agents, iodine as nonmetallic catalyst, and DMSO as both the oxidant and solvent. This method is practical and environmentally benign in terms of sulfur sources, catalyst, and solvent. The catalytic reaction is selective at the C3 position of indoles and compatible with a wide range of substrates, giving the desired products in good to excellent yields.

A tetra-n-butylammonium iodide mediated reaction of indoles with Bunte salts: efficient 3-sulfenylation of indoles under metal-free and oxidant-free conditions

A highly efficient TBAI triggered procedure for 3-sulfenylation of indoles with Bunte Salts under metal-free and oxidant-free conditions is demonstrated.

Microwave-assisted synthesis of 3-sulfenylindoles by sulfonyl hydrazides using organic ionic base-Brønsted acid

3-Sulfenylation of indoles by sulfonyl hydrazides using organic ionic base-Bronsted acid sulfonyl hydrazides as thiol surrogate.

Generation of thioethers via direct C–H functionalization with sodium benzenesulfinate as a sulfur source

A novel ammonium iodide-induced sulfenylation method of flavones, indole and arylimidazo[1,2-a]pyridines using stable and odorless sodium benzenesulfinates as sulfur sources was developed, generating regioselective derivatives in good yields.

Microwave-assisted regioselective sulfenylation of indoles under solvent- and metal-free conditions

Formation of 3-sulfenylindoles using sulfinic acid as a sulfenylating agent.

Tandem approach for the synthesis of 3-sulfenylimidazo[1,5-a]pyridines from dithioesters

Iodine-mediated synthesis of 3-sulfenylimidazo[1,5-a]pyridines via C–H functionalization has been achieved using dithioesters, 2-methylaminopyridines and sulfonyl hydrazides.

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.

Manganese catalysed sulfenylation of N-methyl amides with arenesulfonyl hydrazides

A convenient oxidative sulfenylation method for the formation of various sulfenyl amides has been reported.

DMSO as oxidant and sulfenylating agent for metal-free oxidation and methylthiolation of alcohol-containing indoles

A new methylthiolation protocol was successfully established for the synthesis of substituted indoles bearing 3-methylthioether moiety, in which new C–S bond and C=O bond were formed using dimethyl sulfoxide as the sulfur source under mild conditions.

Metal- and base-free syntheses of aryl/alkylthioindoles by the iodine-induced reductive coupling of aryl/alkyl sulfonyl chlorides with indoles

Iodine-induced reductive coupling of aryl/alkyl sulfonyl chlorides with indoles leading to various substituted aryl/alkylthioindoles has been accomplished.

Iodine-catalyzed regioselective thiolation of imidazo[1,2-a]pyridines using sulfonyl hydrazides as a thiol surrogate

Iodine-catalyzed regioselective sulfenylation of imidazo[1,2-a]pyridines via C(sp²)–H bond functionalization has been achieved using sulfonyl hydrazides as a thiol surrogate.

A solvent- and metal-free synthesis of 3-chacogenyl-indoles employing DMSO/I2 as an eco-friendly catalytic oxidation system

Herein, we describe a solvent- and metal-free method for the synthesis of 3-chalcogenyl-indoles from indoles and diorganyl dichalcogenides using an equivalent amount of DMSO as an oxidant, under catalysis by molecular iodine. This mild and eco-friendly approach allowed the preparation of a wide range of 3-selenyl- and 3-sulfenyl-indoles in good to excellent yields.

Palladium-catalyzed thiolation of alkanes and ethers with arylsulfonyl hydrazides

A new method for the preparation of alkyl aryl sulfides through direct oxidative thiolation of alkanes or ethers with arylsulfonyl hydrazides using DTBP as an oxidant catalyzed by Pd(OAc)₂ has been reported. The C–H bonds in various alkanes or ethers were successfully converted into C–S bonds with moderate to good yields.

Cs2CO3 promoted direct C–H bond sulfenylation of imidazo[1,2-a]pyridines and related heteroarenes in ionic liquid

Cs₂CO₃-promoted sulfenylation of imidazo[1,2-a]pyridines in ionic liquid.

K2S2O8/arenesulfinate: an unprecedented thiolating system enabling selective sulfenylation of indoles under metal-free conditions

Direct selective sulfenylation of indoles is disclosedviaan unprecedented deoxygenation of arylsulfonyl radical only under K₂S₂O₈/arenesulfinate system in CH₃CN/H₂O.