Mechanistic Insight into the Cu-Catalyzed C-S Cross-Coupling of Thioacetate with Aryl Halides: A Joint Experimental-Computational Study

Electronic Effects in a Green Protocol for (Hetero)Aryl-S Coupling

Aryl and heteroaryl iodides have been efficiently converted into the corresponding thioacetates in cyclopentyl methyl ether (CPME), a green solvent, under Cu catalysis. The chemoselectivity of the reaction is mainly controlled by electronic factors, enabling the conversion of both electron-rich and electron-deficient substrates into the corresponding thioacetates in good to excellent yields. The products can be easily deprotected to the corresponding thiolates to carry out additional synthetic transformations in situ. Surprisingly, despite CPME's relatively low dielectric constant, the reaction rate significantly increased when conducted under microwave irradiation conditions. This synthetic methodology exhibits a remarkable tolerance to functional groups, mild reaction conditions, and a wide substrate scope, utilizing a safe and inexpensive CuI pre-catalyst in the green solvent CPME. A non-aqueous workup allowing for the complete recovery of both catalyst and solvent makes this approach an environmentally sustainable protocol for C(sp2) sulfur functionalization. Additionally, the reaction shows selective cross-coupling with iodides in competition with chlorides and bromides, allowing its use in multistep syntheses. To demonstrate the potential of this methodology, it was applied to the high-yield synthesis of a photochromic dithienylethene, where a selective synthesis had not been reported before.

One-pot synthesis of 11-sulfenyl dibenzodiazepines via tandem sulfenylation/cyclization of o-isocyanodiaryl amines and diaryl disulfides

A one-pot sulfenylation/cyclization of o-isocyanodiaryl amines has been described for the preparation of 11-sulfenyl dibenzodiazepines. This AgI-catalyzed reaction covers an unexplored tandem process to give seven-membered N-heterocycles. This transformation shows a broad range of substrate scope, simple operation, and moderate to good yields under aerobic conditions. Diphenyl diselenide can also be produced in an acceptable yield.

Visible-Light-Driven Thioesterification of Aryl Halides with Potassium Thiocarboxylates: Transition-Metal Catalyst-Free Incorporation of Sulfur Functionalities into an Aromatic Ring

Reactions of acceptor-substituted aryl iodides and bromides with potassium thiocarboxylates under white light irradiation allow for the preparation of S-aryl thioesters including synthetically versatile S-aryl thioacetates. This transition-metal and external photocatalyst-free method features extremely mild reaction conditions compared with those used in transition-metal-catalyzed protocols. Reactions proceed via the initial formation of an electron donor-acceptor (EDA) complex in the ground state, which was supported by UV-vis spectra. Electron paramagnetic resonance (EPR) spin-trapping experiments using phenyl-N-tert-butylnitrone (PBN) have revealed the radical nature of the reaction.

Design of Bis(1,10-phenanthroline) Copper(I)-Based Mechanochromic Indicators

In the growing field of single-molecule mechanochromism, the potential of transition metal complexes is yet to be examined. In this work, we have synthesized a series of [Cu(phen)₂]⁺ complexes: bis-Cu(I)-phenanthroline, bis-Cu(I)-phenanthroline-2-amine, and bis-Cu(I)-phenanthroline-2-acetamide. After that, we characterized the complexes by UV-vis spectroscopy and employed density functional theory (DFT) calculations to investigate the changes in UV-vis upon mechanical pulling via force calculations. The results of our examination of time-dependent (TD)-DFT-calculated UV-vis suggests that the bis-Cu(I)-phenanthroline-2-acetamide complex is predicted to have an observable shift of the metal-to-ligand charge transfer band upon pulling from 0 to 0.6 nN in the visible region. We have demonstrated the ability to synthesize and characterize bis-Cu(I)-phenanthroline-2-acetamide. In addition, the TD-DFT calculations predict an observable shift in the visible region of the UV-vis spectrum. This indicates that transition metal complexes are feasible candidates as mechanophores and are worthy of further exploration as to their potential role in a new subclass of mechanochromic indicators.

Thiolate-assisted copper(i) catalyzed C–S cross coupling of thiols with aryl iodides: scope, kinetics and mechanism

The scope and mechanism of the C–S cross coupling of thiophenols with aryl iodides using a Cu(i) catalyst in a ligand-free environment is disclosed.

Recent advances in visible light-activated radical coupling reactions triggered by (i) ruthenium, (ii) iridium and (iii) organic photoredox agents

Photoredox chemistry with organic or transition metal agents has been reviewed in earlier years, but such is the pace of progress that we will overlap very little with earlier comprehensive reviews. This review first presents an overview of the area of research and then examines recent examples of C-C, C-N, C-O and C-S bond formations via radical intermediates with transition metal and organic radical promoters. Recent successes with Birch reductions are also included. The transition metal chemistry will be restricted to photocatalysts based on the most widely used metals, Ru and Ir, but includes coupling chemistries that take advantage of low-valent nickel, or occasionally copper, complexes to process the radicals that are formed. Our focus is on developments in the past 10 years (2011-2021). This period has also seen great advances in the chemistry of organic photoredox reagents and the review covers this area. The review is intended to present highlights and is not comprehensive.

Computational Insight into Cu-Catalyzed Csp-S Coupling to Form a Macrocyclic Alkynyl Sulfide

Copper-catalyzed C_sp-S cross-coupling is known to form rare macrocyclic alkynyl sulfides. Computational studies now suggest a mechanism for the reaction pathway. Upon formation of Cu-S species, subsequent α-addition/elimination at the ethynylic carbon affords the desired macrocycle.

Mechanistic understanding of the Cu(i)-catalyzed domino reaction constructing 1-aryl-1,2,3-triazole from electron-rich aryl bromide, alkyne, and sodium azide: a DFT study

The mechanism of the Cu(i)-catalyzed domino reaction furnishing 1-aryl-1,2,3-triazole assisted by CuI and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) is explored with density functional theory (DFT) calculations.

Cu(I)/sucrose-catalyzed hydroxylation of arenes in water: the dual role of sucrose

A protocol for the hydroxylation of aryl halides catalyzed by copper(i) and sucrose in neat water has been developed. The dual role of sucrose, the reaction pathway, and the high selectivity for hydroxylation were investigated using a combination of experimental and theoretical techniques.

Ullmann-type C-Se Cross-Coupling in the Hydantoin Family: Synthesis, Mechanistic Studies, and Tests of Biological Activity

An attractive strategy for C-Se bond formation by Ullmann-type copper(I)-promoted cross-coupling is developed. A wide range of aryliodides reacts with various disubstituted 2-selenohydantoins under mild conditions and provides Se-arylated imidazolines in moderate to high yields. Computational mechanistic studies show the oxidative addition/intramolecular reductive elimination likely to be the lowest-energy pathway. Cytotoxic activity of all 43 reaction products has been tested in vitro against MCF7 and A549 cancer cell lines with VA13 and MCF10a control cells.

Innovative Three-Step Microwave-Promoted Synthesis of N-Propargyltetrahydroquinoline and 1,2,3-Triazole Derivatives as a Potential Factor Xa (FXa) Inhibitors: Drug Design, Synthesis, and Biological Evaluation

The coagulation cascade is the process of the conversion of soluble fibrinogen to insoluble fibrin that terminates in production of a clot. Factor Xa (FXa) is a serine protease involved in the blood coagulation cascade. Moreover, FXa plays a vital role in the enzymatic sequence which ends with the thrombus production. Thrombosis is a common causal pathology for three widespread cardiovascular syndromes: acute coronary syndrome (ACS), venous thromboembolism (VTE), and strokes. In this research a series of N-propargyltetrahydroquinoline and 1,2,3-triazole derivatives as a potential factor Xa (FXa) inhibitor were designed, synthesized, and evaluated for their FXa inhibitor activity, cytotoxicity activity and coagulation parameters. Rational design for the desired novel molecules was performed through protein-ligand complexes selection and ligand clustering. The microwave-assisted synthetic strategy of selected compounds was carried out by using Ullmann-Goldberg, N-propargylation, Mannich addition, Friedel-Crafts, and 1,3-dipolar cycloaddition type reactions under microwave irradiation. The microwave methodology proved to be an efficient way to obtain all novel compounds in high yields (73–93%). Furthermore, a thermochemical analysis, optimization and reactivity indexes such as electronic chemical potential (µ), chemical hardness (η), and electrophilicity (ω) were performed to understand the relationship between the structure and the energetic behavior of all the series. Then, in vitro analysis showed that compounds 27, 29–31, and 34 exhibited inhibitory activity against FXa and the corresponding half maximal inhibitory concentration (IC₅₀) values were calculated. Next, a cell viability assay in HEK293 and HepG2 cell lines, and coagulation parameters (anti FXa, Prothrombin time (PT), activated Partial Thromboplastin Time (aPTT)) of the most active novel molecules were performed to determine the corresponding cytotoxicity and possible action on clotting pathways. The obtained results suggest that compounds 27 and 29 inhibited FXa targeting through coagulation factors in the intrinsic and extrinsic pathways. However, compound 34 may target coagulation FXa mainly by the extrinsic and common pathway. Interestingly, the most active compounds in relation to the inhibition activity against FXa and coagulation parameters did not show toxicity at the performed coagulation assay concentrations. Finally, docking studies confirmed the preferential binding mode of N-propargyltetrahydroquinoline and 1,2,3-triazole derivatives inside the active site of FXa.

Is Cu(iii) a necessary intermediate in Cu-mediated coupling reactions? A mechanistic point of view

The different pathways have been summarized to disclose the key intermediate in copper-mediated coupling reactions.

Efficient one-pot green synthesis of tetrakis(acetonitrile)copper(i) complex in aqueous media

New simple, fast, effective and environmentally friendly one-pot method for the synthesis of extensively used tetrakis(acetonitrile)copper(i) complexes with BF₄⁻, PF₆⁻ and ClO₄⁻ counterions is invented and optimized. The approach suggested allows using water as solvent and minimizes amounts of toxic organic reagents in the synthetic protocol.

New simple, fast, effective and environmentally friendly one-pot method for the synthesis of extensively used tetrakis(acetonitrile)copper(i) complexes with BF₄⁻, PF₆⁻ and ClO₄⁻ counterions is invented and optimized.

Oxalic Diamides and tert-Butoxide: Two Types of Ligands Enabling Practical Access to Alkyl Aryl Ethers via Cu-Catalyzed Coupling Reaction

A robust and practical protocol for preparing alkyl aryl ethers has been developed, which relies on using two types of ligands to promote Cu-catalyzed alkoxylation of (hetero)aryl halides. The reaction scope is very general for a variety of coupling partners, particularly for challenging secondary alcohols and (hetero)aryl chlorides. In case of coupling with aryl chlorides and bromides, two oxalic diamides serve as the powerful ligands. The tert-butoxide is first demonstrated as a ligand for Cu-catalyzed coupling reaction, leading to alkoxylation of aryl iodides complete at room temperature. Additionally, a number of carbohydrate derivatives are applicable for this coupling reaction, affording the corresponding carbohydrate-aryl ethers in 29-98% yields.

Theoretical study of C-arylations with aryl halides to determine the reaction mechanism, the effect of substituents and heteroatoms

A set of Ullman-like reaction mechanisms are reported using DFT wB97XD/6-311D.