Copper-Catalyzed Three-Component System for Arylsulfenylation of Imidazopyridines with Elemental Sulfur

Four-Component Ring-Opening Reaction of Pyrroles via C-N Bond Cleavage under Multiple Functions of Elemental Sulfur

We report a four-component ring-opening reaction of pyrroles via C-N bond cleavage. In this process, elemental sulfur is used as the sulfur source of thiazole and thioamide and the reductant of olefin. A series of benzothiazoles functionalized with thiopropionamides at the C2 position were synthesized using this method. A plausible reaction mechanism is proposed based on the concise control experiments.

Selective oxidative β-C-H bond sulfenylation of tetrahydroisoquinolines with elemental sulfur

In this article, a convenient and efficient KIO₃-promoted oxidative sulfenylation at the β-position of tetrahydroisoquinolines and subsequent aromatization in the presence of elemental S₈ is presented. The reaction proceeds with moderate to good yields via a double C-S formation process. A wide range of structurally diverse 4-sulfenylisoquinolines/3-sulfenylpiperidine were synthesized with excellent functional group tolerance and high efficiency.

Anticancer-active 3,4-diarylthiolated maleimides synthesis via three-component radical diarylthiolation

Herein, we report an efficient and simple copper-catalyzed oxidative diarylthiolation of maleimides with sulfur powder and aryl boronic acids, in which S powder was used as a substrate and internal oxidant. The corresponding double C-S bonds coupling products were obtained in moderate to high yields under a simple catalytic system. Mechanistic studies indicated that copper-catalyzed radical thiolation of aryl boronic acids with S powder, and the resulting arylthiyl underwent radical addition with double bonds of maleimides.

Cu-Catalyzed Diarylthiolation of Ynones with Aryl Iodides and Elemental Sulfur: An Access to Tetrasubstituted (Z)-1,2-Bis(arylthio)alkenes and Benzo[b][1,4]dithiines

A copper-catalyzed three-component reaction of ynones, aryl iodides, and elemental sulfur via a syn-addition process is established. The reaction features operational practicality, broad substrate scope, and readily accessible scale-up synthesis by affording a series of (Z)-1,2-bis(arylthio)alkenes in good to excellent yield. Moreover, benzo[b][1,4]dithiines can be also constructed efficiently by using 1,2-diiodobenzene as the coupling partner.

Iodine-Mediated Multicomponent Cascade Cyclization and Sulfenylation/Selenation: Synthesis of Imidazo[2,1-a]isoquinoline Derivatives

A novel multicomponent cascade cyclization and sulfenylation/selenation using aryl methyl ketones, isoquinolin-1-amine, and sodium arylsulfinates/1,2-diphenyldiselane to synthesize imidazo[2,1-a]isoquinoline derivatives in one-pot via the construction of two C-N bonds and one C-S/C-Se bond has been reported. This multicomponent reaction realizes simultaneous C(sp³)-H amination and sulfenylation/selenation, avoiding complicated prior substrate preparation. This process has simple operating conditions and good substrate compatibility.

Diethylaminosulfur Trifluoride: A Novel, Low-Cost, Stable Double Thiolation Reagent for Imidazo[1,2-α]pyridines

We report a novel, inexpensive double thiolation reagent that sulfurizes a broad range of imidazo[1,2-α]pyridines under mild conditions. Importantly, diethylaminosulfur trifluoride, as a common nucleophilic fluorinating reagent, was utilized as a novel thiolation reagent.

A review on the role of transition metals in selenylation reactions

Organoselenium chemistry has emerged as a distinctive area of research with tremendous utility in the synthesis of biologically and pharmaceutically active molecules. Significant synthetic approaches have been made for the construction of C-Se bonds which find use in other organic transformations. This review focuses on the versatility of transition metal-mediated selenylation reactions, providing insights into various synthetic pathways and mechanistic details. Further, this review aims to offer a broad perspective for designing efficient and novel catalysts to incorporate organoselenium moiety into the inert C-H bonds.

Iodine-catalyzed sulfuration of isoquinolin-1(2H)-ones applying ethyl sulfinates

Sulfuration of isoquinolin-1(2H)-ones at the C-4 position by employing ethyl sulfonates.

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.

Catalyst and additive-free oxidative dual C-H sulfenylation of imidazoheterocycles with elemental sulfur using DMSO as a solvent and an oxidant

Dual C-H sulfenylation was used to obtain 3-vulcanized imidazoheterocycles using odorless elemental sulfur under catalyst- and additive-free conditions. C-H activation of both imidazoheterocycles and arylamines/arenols/indoles was realized by a practical protocol in which DMSO served as both a solvent and an internal oxidant.

Copper-catalyzed diastereoselective hydrothioetherification of oxa(aza)benzonorbornadienes

A novel copper-catalyzed hydrothioetherification of oxa(aza)bicyclic alkenes with potassium thioacetate and aryl or alkyl iodides to synthesize unsymmetrical thioethers has been developed. Notably, the reaction with complete diastereoselectivity went through a syn-selective addition process to give exo-adducts. In addition, this protocol exhibited high efficiency and good functional group tolerance to afford the target thioethers in moderate to good yields. Based on the results of mechanistic investigations, a plausible mechanism was proposed.

Direct Sulfenylation of the Purine C8-H Bond with Thiophenols

The one-step copper-mediated regioselective formation of the C₈-S bond for purine derivatives with arylthiols was achieved using air as the green oxidant in the presence of 1.0 equiv of Na₂CO₃ and stoichiometric CuCl and 1,10-phenanthroline monohydrate. This method provides an economical, easy-to-handle, and effective method for the synthesis of 8-sulfenylpurine derivatives in moderate to excellent yields. The reaction is selective for C8 over C2 and C6. It also tolerates a free amine on the purine, and it has a wide substrate scope.

Annulation of imidazo[1,2-a]pyridines under metal-free conditions

Synthesis of benzo[a]imidazo[5,1,2-cd]indolizines from 2-arylimidazo[1,2-a]pyridines and benzyne precursors under metal-free conditions has been described.

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.

Advances in Cu and Ni-catalyzed Chan–Lam-type coupling: synthesis of diarylchalcogenides, Ar2–X (X = S, Se, Te)

Advances in the Cu and Ni-catalyzed Chan–Lam-type coupling of aryl/heteroarylboronic acids with various chalcogen sources for diarylsulfide, diarylselenide and diaryltelluride synthesis are covered in this review.

Catalyst-free direct cross-dehydrogenative coupling of imidazoheterocycles with glyoxal hydrates: an efficient approach to 1,2-diketones

An efficient and convenient methodology for catalyst-free cross-dehydrogenative coupling of imidazoheterocycles with glyoxal hydrates in good yields was developed. This methodology exhibits a broad substrate scope and excellent functional group tolerance and offers a straightforward means to produce different heterocycles such as imidazoheterocyclic quinoxaline, imidazoheterocyclic hydantoin and imidazoheterocyclic α-keto ketamine under relatively mild conditions. Biological evaluation showed that the most potent compound 3m possesses significant in vitro antiproliferative activities against human-derived lung cancer cell lines with an IC50 value of 14.8 μM.

Copper-Catalyzed Tandem Sulfuration/Annulation of Propargylamines with Sulfur via C-N Bond Cleavage

Copper-catalyzed aerobic oxidative sulfuration and annulation of propargylamines with elemental sulfur is described. The tandem reaction involves C-N bond cleavage and the formation of multiple C-S bonds, affording 1,2-dithiole-3-thiones in good to excellent yields with good functional group tolerance.

Iodine-promoted radical alkyl sulfuration of imidazopyridines with dialkyl azo compounds and elemental sulfur

Dialkyl azo compounds were found to be effective alkyl radical sources for direct alkyl sulfuration with imidazopyridines using elemental sulfur under metal-free conditions. Iodine, an inexpensive and mild reagent, could promote alkyl sulfuration. A variety of quaternary cyanoalkyl radicals were successfully coupled with elemental sulfur. A subsequent C-H sulfuration of imidazopyridines afforded a diverse array of imidazopyridine derivatives bearing cyanoalkylthio groups. The cyano group could be modified and further underwent condensation with 2-aminothiazole to afford an interesting heterocyclic amide. Control experiments showed that iodine could greatly suppress the self-coupling of cyanoalkyl radicals, thus making the sulfuration proceed smoothly.

Oxidative dual C–H selenation of imidazoheterocycles with ethers or alkanes using selenium powder via a radical pathway

A DCP-mediated oxidative dual C–H selenation radical reaction of imidazoheterocycles with ethers or alkanes using selenium powder was developed.

Direct access to bis-S-heterocyclesviacopper-catalyzed three component tandem cyclization using S8as a sulfur source

An elemental sulfur atom donor strategy for constructing a thiophene-fused thiazole bis-S-heterocyclic skeletonviaCu-catalyzed three-component tandem cyclization has been developed.

Direct thiocarbamation of imidazoheterocycles via dual C–H sulfurization

Direct thiocarbamation via dual C–H sulfurization.

3d Transition Metals for C-H Activation

C-H activation has surfaced as an increasingly powerful tool for molecular sciences, with notable applications to material sciences, crop protection, drug discovery, and pharmaceutical industries, among others. Despite major advances, the vast majority of these C-H functionalizations required precious 4d or 5d transition metal catalysts. Given the cost-effective and sustainable nature of earth-abundant first row transition metals, the development of less toxic, inexpensive 3d metal catalysts for C-H activation has gained considerable recent momentum as a significantly more environmentally-benign and economically-attractive alternative. Herein, we provide a comprehensive overview on first row transition metal catalysts for C-H activation until summer 2018.

K₂S₂O₈-Promoted Aryl Thioamides Synthesis from Aryl Aldehydes Using Thiourea as the Sulfur Source

Thiourea as a sulfur atom transfer reagent was applied for the synthesis of aryl thioamides through a three-component coupling reaction with aryl aldehydes and N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMAC). The reaction could tolerate various functional groups and gave moderate to good yields of desired products under the transition-metal-free condition.