Microwave‐Assisted Cross‐Coupling for the Construction of Diaryl Sulfides

The construction of diaryl sulfides through the cross‐coupling of aryl iodides and thiols in microwave heating is described. By using this method, a variety of diaryl sulfides can be prepared in a mild condition and in high yields. Deactivated 4‐nitrothiophenol was effective to afford the product in 94% yield. Sterically hindered ortho‐substituted aryl iodides or thiophenols provided diaryl sulfides effectively by this microwave‐assisted coupling reaction.     

Copper mediated coupling of 2-(piperazine)-pyrimidine iodides with aryl thiols using Cu(I)thiophene-2-carboxylate

A copper-mediated synthesis of diaryl sulfides utilizing Cu(I)-thiophene-2-carboxylate (CuTC) is described. We demonstrate the use of CuTC as a soluble, non-basic catalyst in the coupling of aryl iodides and aryl thiols in the synthesis of synthetically advanced diaryl sulfides. This method allows for the successful coupling of challenging substrates including ortho-substituted and heteroaryl iodides and thiols. Additionally, most of the aryl iodide substrates used here contain the privileged piperazine scaffold bound to a pyrimidine, pyridine, or phenyl ring and thus this method allows for the elaboration of complex piperazine scaffolds into molecules of biological interest. The method described here enables the incorporation of late-stage structural diversity into diaryl sulfides containing the piperazine ring, thus enhancing the number and nature of derivatives available for SAR investigation.     

Simple and efficient copper-catalyzed S-arylation of diaryl disulfides with triarylbismuthanes under aerobic conditions

Novel and simple copper-catalyzed C(aryl)-S bond formation of diaryl disulfides with bismuth reagents is described. Reactions of diaryl disulfides with triarylbismuthanes in the presence of CuOAc (10 mol %) and 1,10-phenanthroline (10 mol %) under aerobic conditions led to the formation of unsymmetrical diaryl sulfides in satisfactory yields. The reaction is atom-economic and all three aryl groups of the triarylbismuthanes and both sulfanyl groups of the diaryl disulfides could be transferred to the coupling products.     

Efficient ligand-free copper-catalyzed C-S cross-coupling of thiols with aryl iodides using KF/Al2O3 as base

We report a mild, convenient, environmentally friendly, and ligand-free synthetic protocol for the cross-coupling reaction of aryl iodides and thiols using 10 mol % CuI with KF/Al₂O₃ as the base, in DMF at 110 °C. Using this protocol, we have shown that a variety of aryl sulfides can be synthesized in excellent yields from readily available iodides and thiols.     

One-pot synthesis of symmetrical and unsymmetrical aryl sulfides by Pd-catalyzed couplings of aryl halides and thioacetates

Aryl sulfides were obtained from the coupling reaction of S-aryl (or S-alkyl) thioacetates and aryl bromides in the presence of palladium catalyst. This reaction method enables the one-pot synthesis of symmetrical and unsymmetrical diaryl sulfides by employing potassium thioacetate with aryl iodides and aryl bromides.     

A general rhodium-catalyzed cross-coupling reaction of thiols with aryl iodides

The general procedure for the rhodium-catalyzed cross-coupling of thiols with aryl iodides is described. The catalytic system consists of 5 mol % of [RhCl(cod)]₂ and 10 mol % of PPh₃ as a ligand. A variety of aryl iodides reacted with thiols, giving aryl thioethers in good to excellent yields. It is important to note that the deactivated aryl iodides such as 4-iodoanisole is worked smoothly to provide the corresponding aryl thioethers in excellent yields. Functional groups such as free-amines, chloro, are all tolerated under the employed reaction conditions.     

Convenient copper- and solvent-free Sonogashira-type alkynylation of aryl iodides and bromides using Pd EnCat™

A straightforward methodology is described for the copper- and solvent-free alkynylations of aryl iodides and bromides using 0.1-0.01 mol % of Pd as Pd EnCat™ 40 or TPP30. High yielding reactions can be achieved under aerobic conditions for a variety of activated and deactivated aryl iodides; a few examples with aryl bromides are also described. Microwave irradiation is able to enhance yields and rates of these reactions.     

Copper-catalyzed cross-coupling of sulfonamides with aryl iodides and bromides facilitated by amino acid ligands

A highly general, convenient, and inexpensive catalyst system was developed for the N-arylation of sulfonamides with aryl iodides or bromides by using 5-20 mol % of CuI as catalyst, 20 mol % of N-methylglycine (for aryl iodides) or N,N-dimethylglycine (for aryl bromides) as ligand, and K₃PO₄ as base.     

Efficient copper-catalyzed coupling of aryl iodides and thiobenzoic acid

A highly efficient copper-catalyzed coupling reaction of aryl iodides and thiobenzoic acid, using 10 mol % of copper iodide, 20 mol % of 1,10-phenanthroline, and ⁱPr₂NEt in toluene, was developed. This methodology is applicable to a variety of aryl iodides.     

Development of a room temperature Hirao reaction

Arylphosphonates were prepared at 25 °C through the palladium-catalyzed coupling of aryl iodides with a silver phosphonate. A wide range of aryl iodides were successfully employed including phenolic substrates as well as those containing an ortho substituent.     

A copper- and amine-free Sonogashira coupling reaction promoted by a ferrocene-based phosphinimine-phosphine ligand at low catalyst loading

A palladium(II) complex containing a ferrocene-based phosphinimine-phosphine ligand was applied to the amine- and copper-free Sonogashira coupling of aryl iodides and aryl bromides with terminal alkynes using 1 equiv of tetrabutylammonium acetate as an activator. The corresponding disubstituted alkynes were obtained in high yields and TONs using 0.1 mol % Pd-catalyst.     

Electron transfer activity of a cobalt crown carbene complex

The novel cobalt(II) crown carbene complex 12(II) has been prepared and characterised by X-ray crystallography. This complex is reduced in a one-electron process to a cobalt(I) complex that acts as a powerful single electron donor, reducing aryl halides, including aryl chlorides and demonstrating the strong electron-enriching effect on cobalt of the crown carbene ligand. The metal ion is tightly held in a tetrahedral conformation by its enveloping crown ligand—this prevents what would otherwise be expected to be an easy oxidation to cobalt(III) under standard electrochemical conditions. Complex 12 is shown to be an effective catalyst in mediated electrochemical reductions of aryl iodides at room temperature and aryl bromides at 90 °C. The electrochemically produced catalyst [from 10 mol % of added Co(II) complex] also triggers reduction of aryl chlorides, although this seems at the limit of its reactivity. However, when the cobalt(II) complex is reduced by sodium amalgam, this affords stoichiometric quantities of the active cobalt reducing agent, which affords reduction of aryl iodides and bromides as above, but also reduces aryl chlorides at elevated temperatures.     

Aerobic ligand-free Suzuki coupling catalyzed by in situ-generated palladium nanoparticles in water

A simple and efficient procedure for Suzuki coupling of aryl bromides/iodides with aryl- and alkylboronic acids catalyzed by in situ-generated palladium(0) nanoparticles in water without any ligand in open air to produce a variety of functionalized biaryls and alkyl-aryls has been developed. The boronic acids act here as the reducing agent for the formation of Pd nanoparticles. The reactions are remarkably fast (5 min) and high yielding. The catalyst is recyclable up to three runs without loss of efficiency.     

Efficient Copper(I)‐Catalyzed S‐Arylation of KSCN with Aryl Halides in PEG‐400

A simple and efficient protocol for CuI‐catalyzed C? S bond formation of aryl halides with KSCN to symmetrical diaryl sulfides was reported in PEG‐400 without any other additives. A variety of aryl halides were converted to the corresponding diaryl sulfides in good to excellent yields. The present procedure tolerated a variety of functional groups and the steric hindrance of ortho‐substituents on aryl halides did not affect the outcome.     

Amino acid-mediated Goldberg reactions between amides and aryl iodides

A highly general, experimentally simple, and inexpensive catalyst system was developed for the amidation of aryl iodides by using 5 mol % of CuI as catalyst, 20 mol % of an amino acid as ligand, and K₃PO₄ as base.     

A general method for the formation of diaryl selenides using copper(I) catalysts

We report a mild, palladium-free synthetic protocol for the cross coupling reaction of aryl iodides and phenyl selenol using 10 mol% CuI/neocuproine, NaOt-Bu or K₂CO₃ as base, in toluene, at 110°C. Using this protocol, we show that a variety of diaryl selenides can be synthesized in good yields from commercially available aryl iodides.     

Palladium-catalyzed cyanation of aryl halides using K4[Fe(CN)6] as cyanide source, water as solvent, and microwave heating

A methodology for the cyanation of aryl iodides and activated aryl bromides is reported using water as the solvent and K₄[Fe(CN)₆] as the cyanide source. Reactions are complete within 20 min.     

Ligand‐free copper‐catalysed direct synthesis of diaryl sulfides and diaryl disulfides in wet poly(ethylene glycol)

An improved protocol has been developed for the one‐pot CuI‐catalysed preparation of symmetric diaryl sulfides from their available aryl halides in the presence of thiourea as sulfur transfer agent and in the absence of both ligand and organic solvent. This catalytic system was also used for the high‐yielding preparation of diaryl disulfides in the presence of C₂Cl₆ as oxidant.     

MODERN FRIEDEL–CRAFTS CHEMISTRY. XIV. ON THE CYCLIZATION OF SELECTED ARYL HYDROXYALKYL SULFIDES

Abstract

The feasibility of cycloalkylation reactions in the presence of Friedel–Crafts catalysts was demonstrated in a number of aryl hydroxyalkyl sulfides (1–5), and benzyl hydroxyalkyl sulfides (6–7). Treatment of compounds (1–7) with Friedel-Crafts catalysts gave diaryl disulfides, diaryl sulfides, arene thiols, chlorohydrins, aryl chloroalkyl sulfides, aryl alkenyl sulfides and cyclization products. It is noteworthy to mention that cyclization products were isolated only in cases where the hydroxyl group is linked to a tertiary carbon atom as in compounds 3 and 7.

A suitable reaction pathway is suggested to rationalize the formation of the various reaction products.     

Visible-light-promoted synthesis of diaryl sulfides under air

A convergent, organocatalytic visible-light-mediated process for the synthesis of diaryl sulfides has been developed. A broad range of aryl thiols reacted with various aryl diazonium salts in the presence of eosin Y under air atmosphere to afford the desired diaryl sulfides in high yields. This novel and environmentally friendly method provides an alternative route to established synthetic approaches.