Regioselective Sulfenylation Research Articles

KBrO3-Promoted Cross-Dehydrogenative Coupling Reaction: An Odorless Regioselective Sulfenylation of Imidazoheterocycles in Water.

A regioselective metal-free sulfenylation of imidazoheterocycles with heterocyclic thiols or thiones has been achieved using a cross-dehydrogenative coupling method in water. In addition, the procedure has several advantages including green solvents, free of foul-smelling sulfur sources, and mild conditions, thus providing considerable application potential in the pharmaceutical industry.

Visible-Light-Induced Regioselective C-H Sulfenylation of Pyrazolo[1,5-a]pyrimidines via Cross-Dehydrogenative Coupling.

A visible-light-induced cross-dehydrogenative methodology has been developed for the regioselective sulfenylation of pyrazolo[1,5-a]pyrimidine derivatives. Rose bengal, blue LEDs, KI, K2S2O8, and DMSO are all essential for this photocatalytic transformation. The protocol is applicable for the synthesis of a library of 3-(aryl/heteroaryl thio)pyrazolo[1,5-a]pyrimidine derivatives with broad functionalities. The selectivity and scalability of the methodology have been also demonstrated. Moreover, the efficiency of this strategy for sulfenylation of pyrazoles, indole, imidazoheterocycles, and 4-hydroxy coumarin has been proven. The mechanistic investigation revealed the radical-based mechanism and formation of diaryl disulfide as a key intermediate for this cross-dehydrogenative coupling reaction.

Synthesis of novel imidazopyridine-oxadiazole molecular hybrids by a regioselective sulfenylation of imidazo[1,2-a]pyridines with 1,3,4-oxadiazole-2-thiols using I2-FeCl3 catalytic system and O2/air as co-oxidant

Synthesis of novel imidazopyridine-oxadiazole molecular hybrids by a regioselective sulfenylation of imidazo[1,2-a]pyridines with 1,3,4-oxadiazole-2-thiols using I2-FeCl3 catalytic system and O2/air as co-oxidant

Electrochemical Regioselective Sulfenylation of 2H-Indazoles with Thiols in Batch and Continuous Flow.

A novel electrochemical cross-dehydrogenative C-S bond coupling of aryl thiols with 2H-indazole is reported. Thiol-functionalized 2H-indazoles were synthesized under catalyst-, oxidant-, and metal-free conditions with innocuous hydrogen as the sole byproduct at ambient temperature. Furthermore, continuous electrochemical flow conditions using a graphite/Ni flow cell were used to obtained 3-(arylthio)-2H-indazole compounds on a gram scale within the residence time of 39 min. Detailed mechanistic studies including control experiments and cyclic voltammetry are provided to support the radical-radical cross-coupling pathway.

Iodine catalyzed regioselective sulfenylation of aminouracils with sulfonyl hydrazides

A simple protocol is reported for the C5-sulfenylation of aminouracils with sulfonyl hydrazides in the presence of catalytic molecular iodine. The products were easily obtained in good to high yields by filtration. The present method offers an environmentally benign, metal- and oxidant-free alternative route to such compounds which otherwise require the use of thiols, and also an oxidant in some cases.

Hydrogen‐Bonding‐Network‐Assisted Regioselective Trifluoromethylthiolation and Sulfenylation of Electron‐Rich (Hetero)arenes

AbstractWe have developed an efficient and straightforward hydrogen‐bonding‐network‐assisted regioselective sulfenylation and trifluoromethylthiolation of electron‐rich arenes using the electrophilic SCF3 reagent and N‐thiosuccinimides. This catalyst‐free protocol offers good yields for a wide range of arenes and shows good functional group tolerance without any protecting groups.

One-Pot, Three-Component Synthesis of 5-Sulfenyl-2-iminothiazolines by Cross-Dehydrogenative C-S Coupling Using I2/DMSO in Open Air.

A one-pot, three-component, transition-metal-free regioselective sulfenylation of 2-iminothiazoline through the cross-dehydrogenative coupling strategy via sp2 C-H functionalization has been developed employing iodine as a catalyst and dimethyl sulfoxide as an oxidant. Utility of this sulfenylation technique has been well depicted through participation of various aryl and heterocyclic thiols. Significant features of this C-H functionalization strategy include metal-free open air reaction conditions, which offer a mild and efficient method for sulfenylation to achieve diversely substituted 5-sulfenyl-2-iminothiazoline derivatives.

Regioselective Sulfenylation of α'-CH3 or α'-CH2 Groups of α,β-Unsaturated Ketones with Heterocyclic Thiols.

A rare regioselective sulfenylation of α'-CH3 or α'-CH2 bonds adjacent to α,β-unsaturated ketones using dimethyl sulfoxide as an oxidant and a substoichiometric amount of aq HI as an additive is described. This methodology employs a strong acid such as aq HI or iodine and exhibits a high regioselectivity without undergoing conjugate addition, which is difficult to achieve under the cross dehydrogenative coupling method.

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. The reaction worked smoothly under metal-free conditions and afforded a wide range of sulfenylated 4-anilinocoumarins with potential bioactivity in moderate to excellent yields. This method would expand the still limited scope of synthesis methods for C-S bond formation using Bunte salts.

Iodine-mediated sulfenylation of 4-hydroxycoumarins with sulfonyl hydrazides under aqueous conditions

An efficient, metal-free approach to the synthesis of sulfenylated coumarins based on the iodine catalyzed regioselective sulfenylation of 4-hydroxycoumarins with arylsulfonyl hydrazides was developed under mild conditions in water.

Correction: Visible-light-induced regioselective sulfenylation of imidazopyridines with thiols under transition metal-free conditions

Correction for ‘Visible-light-induced regioselective sulfenylation of imidazopyridines with thiols under transition metal-free conditions’ by Rajjakfur Rahaman et al., Green Chem., 2018, 20, 141–147.

Visible-light-induced regioselective sulfenylation of imidazopyridines with thiols under transition metal-free conditions

Visible-light-induced regioselective sulfenylation of imidazopyridines and indoles with thiols under transition metal-free conditions.

CuI-catalyzed Regioselective Sulfenylation of Indoles with Disulfides

Background: While C-S bonds coupling is playing a crucial role in the syntheses of many biologically active substances, the well concerned C-H functionalization reactions have been barely employed yet in construction of such sulfur compounds. Objective: The primary objective of this study was to expand the application of copper, a cheap metal, to catalyze C-S bond construction reactions of indoles. Methods: We chose copper compounds of various oxidant states as catalysts. Substituted indoles were picked as substrates, and disulfides as sulfur source. The variants of catalyst, solvent and reaction temperature were screened to optimize the reaction condition. After that, we explored the scope of diversely substituted indoles and disulfides substrates of the reaction. Results: The reactions were all smoothly performed to provide corresponding products in good yields. The main product is tunable between C3-sulfenylindoles and C2,3-sulfenylindoles according to the amount of disulfides. C3-sulfenylindoles were synthesized in 85 to 99% yields. C2,3-sulfenylindoles were also fruitfully obtained in from 66 to 98% yields. Conclusion: A facile and efficient method for sulfenylation of indole, which employed CuI as catalyst, to give C3- and C2,3- sulfenylindoles, was presented. Our methodology features easy operation, excellent yields and cheapness of catalyst. Keywords: C-H activation, copper, cross-coupling, heterocycles, sulfenylation, indoles.

TBAI-mediated regioselective sulfenylation of indoles with sulfonyl chlorides in one pot

A versatile method for the synthesis of 3-sulfenylated indoles via TBAI promoted sulfenylation of indoles with sulfonyl chlorides in one pot has been presented. This system features highly regioselective, metal-free, easy operation, and shows a broad functional group tolerance leading to excellent yields. And this reaction could be easily conducted in 10 mmol scale with high effectivity. A plausible mechanism is proposed.

N‐Bromosuccinimide Promoted Direct Thiolation of Imidazoheteroaryl C‐H bonds with Disulfides

AbstractA one‐pot protocol has been demonstrated for the regioselective sulfenylation of imidazoheterocycles with disulfides. In this method, thiols are converted to sulfenyl bromides and reacted with 2‐phenylimidazo [1, 2‐a] pyridines. This simple procedure is highly capable for sulfenylation with readily available starting materials in good to excellent yields under transition metal and base free conditions.

Iodine-catalyzed direct C-H thiolation of imidazo[1,5-a]quinolines for the synthesis of 3-sulfenylimidazo[1,5-a]quinolines.

An iodine-catalyzed regioselective sulfenylation of imidazo[1,5-a]quinolines was developed under metal- and oxidant-free reaction conditions. Using disulfides or thiophenols as sulfenylating agents, 3-sulfenylimidazo[1,5-a]quinoline derivatives were obtained in good to excellent yields with broad functional group tolerance. A multi-component reaction to generate 1-sulfenylated imidazo[1,5-a]pyridines is also described. Preliminary biological evaluation showed that some of the 3-sulfenylated imidazo[1,5-a]quinolines had significant anticancer activity.

Combined experimental/theoretical study on d-glucosamine promoted regioselective sulfenylation of indoles catalyzed by copper

A combined experimental/theoretical investigation on the d-glucosamine promoted sulfenylation of indoles at the C3 position with sodium sulfinates catalyzed by copper is presented.

Iodine Promoted Regioselective α-Sulfenylation of Carbonyl Compounds using Dimethyl Sulfoxide as an Oxidant.

A metal-free regioselective sulfenylation of the α-CH3 group of ketones has been achieved in the presence of the α-CH2 or α-CH group using the cross dehydrogenative (CDC) strategy. Aldehydes also exhibit good selectivity forming the corresponding α-sulfenylated products. This efficient sulfenylation of ketones or aldehydes with thiones or heterocyclic thiols utilizes dimethyl sulfoxide (DMSO) as an oxidant in the presence of iodine. This eco-friendly method uses readily available and inexpensive I2 and DMSO. The application of this methodology has been demonstrated by synthesizing precursors for Julia- Kocienski olefination intermediates.

ChemInform Abstract: Iodine‐Catalyzed Regioselective Sulfenylation of Indoles with Thiols in Water.

AbstractThe title reaction features broad substrate scope, mild reaction conditions, excellent regioselectivity, and excellent yields.

Iodine-Catalyzed Cross Dehydrogenative Coupling Reaction: A Regioselective Sulfenylation of Imidazoheterocycles Using Dimethyl Sulfoxide as an Oxidant.

A regioselective formation of C-S bonds has been achieved using a cross dehydrogenative coupling (CDC) protocol using iodine as a catalyst and dimethyl sulfoxide as an oxidant under green chemistry conditions. This strategy employs the reaction of easily available heterocyclic thiols or thiones with imidazoheterocycles. This protocol provides an efficient, mild, and inexpensive method for sulfenylation of imidazoheterocycles with a diverse range of heterocyclic thiols and heterocyclic thiones.