Copper-catalyzed S-arylation of Furanose-Fused Oxazolidine-2-thiones

The 1,3-oxazolidine-2-thiones (OZTs) are important chiral molecules, especially in asymmetric synthesis. These compounds serve as important active units in biologically active compounds. Herein, carbohydrate anchored OZTs were explored to develop a copper-catalyzed C-S bond formation with aryl iodides. Chemoselective S-arylation was observed, with copper iodide and dimethylethylenediamine (DMEDA) as the best ligand in dioxane at 60–90 °C. The corresponding chiral oxazolines were obtained in reasonable to good yields under relatively mild reaction conditions. This approach is cheap, as using one of the cheapest transition metals, a simple protocol and various functional group tolerance make it a valuable strategy for getting S-substituted furanose-fused OZT. The structures of the novel carbohydrates were confirmed by NMR spectroscopy and an HRMS analysis.

Copper-catalyzed selective oxidation of hydrazones through C(sp3)-H functionalization

A simple and mild protocol for copper-catalyzed oxidation of hydrazones at the α-position has been reported. Various substrates are compatible, providing the corresponding products in moderate to good yields. This strategy provides an efficient and convenient solution for the synthesis of carbonyl hydrazone. A free radical pathway mechanism is suggested for the transformation.

Ruthenium Catalyzed Intramolecular C-X (X=C, N, O, S) Bond Formation via C-H Functionalization: An Overview

Ruthenium catalyzed C-H activation is well known for its high tolerance towards the functional group and broad applicability in organic synthesis and molecular sciences, with significant applications in pharmaceutical industries, material sciences, and polymer industry. In the last few decades, enormous progress has been observed with ruthenium-catalyzed C-H activation chemistry. Notably, the vast majority of the C-H functionalization known in the literature are intermolecular, although the intramolecular variant provides fascinating new structural facet starting from the simple molecular scaffolds. Intramolecular C-H functionalization is atom economical and step efficient, results in less formation of undesired products which is easy to purify. This has created a lot of interest in organic chemistry in developing new synthetic strategies for such functionalization. The focus of this review is to present the relatively unexplored intramolecular functionalization of C-H bonds into C-X (X=C, N, O, S) bonds utilizing versatile ruthenium catalysts, their scope, and brief mechanistic discussion.

Visible-Light Carbon Nitride-Catalyzed Aerobic Cyclization of Thiobenzanilides under Ambient Air Conditions

A metal-free heterogeneous photocatalysis has been developed for the synthesis of benzothiazoles via intramolecular C-H functionalization/C-S bond formation of thiobenzanilides by inexpensive graphitic carbon nitride (g-C₃N₄) under visible-light irradiation. This reaction provides access to a broad range of 2-substituted benzothiazoles in high yields under an air atmosphere at room temperature without addition of a strong base or organic oxidizing reagents. In addition, the catalyst was found to be stable and reusable after five reaction cycles.

Oxidative Sulfonylation of Hydrazones Enabled by Synergistic Copper/Silver Catalysis

A copper/silver-cocatalyzed protocol for oxidative sulfonylation of hydrazones is demonstrated. A wide range of β-ketosulfones and N-acylsulfonamides are directly synthesized in moderate to good yields. Our work provides a viable method for scalable preparation of β-ketosulfone derivatives that have found wide applications in the pharmaceutical industry.

Metal free C-3 chalcogenation (sulfenylation and selenylation) of 4H-pyrido[1,2-a]pyrimidin-4-ones

An expeditious metal free C-3 chalcogenation of 4H-pyrido[1,2-a]pyrimidin-4-one has been devised to synthesize diversely orchestrated 3-ArS/ArSe derivatives in high yields (up to 95%). This operationally simple reaction proceeds under mild reaction conditions, can be executed in gram scale, and also highlights broad functional group tolerance. Preliminary experimental investigation suggests a radical mechanistic pathway for these transformations.

Iodine/DMSO-Promoted Selective Direct Arylthiation of Anilines with Thiols under Metal-Free Conditions

An iodine-promoted divergent thiolation of unprotected anilines with thiols for the synthesis of sulfide anilines has been described. The combinational use of I₂ and DMSO played an important role to realize this kind of transformation without the aid of a metal catalyst and strong oxidants. The reaction selectivity was well controlled to provide mono-, bis-, and trisubstituted diaryl sulfide derivatives. More importantly, iodination and sulfenylation can occur simultaneously to provide useful multifunctionalized iodoaniline products. This method afforded an efficient protocol for the construct C-S and C-I bonds from the C-H bond under mild reaction conditions.

A Mild Synthesis of 2-Substituted Benzothiazoles via Nickel-Catalyzed Intramolecular Oxidative C-H Functionalization

A highly efficient synthetic method for the preparation of 2-aminobenzothiazoles starting from arylthioureas has been reported. By using a nickel catalyst, arylthioureas undergo intramolecular oxidative C-H bond functionalization, giving the desired 2-aminobenzothiazoles in good to excellent yields. This protocol features an inexpensive catalyst, low catalyst loading, mild reaction conditions, a short reaction time, and good to excellent yields, and it can be scaled up easily to a gram scale with almost no yields decreasing.

Recent advances in intramolecular C–O/C–N/C–S bond formationviaC–H functionalization

This review presents the construction of C–X bonds (X = O/N/S) by using intramolecular C–H functionalization for the synthesis of heterocyclic compounds.

Ruthenium Catalyzed Intramolecular C-S Coupling Reactions: Synthetic Scope and Mechanistic Insight

A ruthenium catalyzed intramolecular C-S coupling reaction of N-arylthioureas for the synthesis of 2-aminobenzothiazoles has been developed. Kinetic, isotope labeling, and computational studies reveal the involvement of an electrophilic ruthenation pathway instead of a direct C-H activation. Stereoelectronic effect of meta-substituents on the N-arylthiourea dictates the final regioselective outcome of the reaction.

Combined experimental/theoretical study of d-glucosamine promoted Ullmann-type C–N coupling catalyzed by copper(i): does amino really count?

Ullmann type C–N coupling reaction catalyzed by copper(i) with d-glucosamine derivatives as promoters was studied by means of combined experimental/theoretical investigation.

Microwave-assisted rapid synthesis of sugar-based pyrazole derivatives with anticancer activity in water

A rapid, efficient and green method has been developed for the synthesis of some novel sugar-based pyrazole derivatives in eco-friendly water under microwave irradiation in good yields.

Copper(ii)-catalyzed remote sulfonylation of aminoquinolines with sodium sulfinates via radical coupling

Many various aminoquinolines-derived sulfones were obtained in moderate to high yields via copper(ii)-catalyzed direct C(sp²)–H sulfonylation of aminoquinolines with sodium sulfinates.

Efficient Ullmann C–N coupling catalyzed by a recoverable oligose-supported copper complex

The recoverable oligose-supported copper complex as catalyst for an Ullmann-type C–N coupling reaction of N-nucleophiles and aryl halides under mild conditions.

On the Critical Effect of the Metal (Mo vs. W) on the [3+2] Cycloaddition Reaction of M3 S4 Clusters with Alkynes: Insights from Experiment and Theory

Whereas the cluster [Mo3 S4 (acac)3 (py)3 ](+) ([1](+) , acac=acetylacetonate, py=pyridine) reacts with a variety of alkynes, the cluster [W3 S4 (acac)3 (py)3 ](+) ([2](+) ) remains unaffected under the same conditions. The reactions of cluster [1](+) show polyphasic kinetics, and in all cases clusters bearing a bridging dithiolene moiety are formed in the first step through the concerted [3+2] cycloaddition between the C≡C atoms of the alkyne and a Mo(μ-S)2 moiety of the cluster. A computational study has been conducted to analyze the effect of the metal on these concerted [3+2] cycloaddition reactions. The calculations suggest that the reactions of cluster [2](+) with alkynes feature ΔG(≠) values only slightly larger than its molybdenum analogue, however, the differences in the reaction free energies between both metal clusters and the same alkyne reach up to approximately 10 kcal mol(-1) , therefore indicating that the differences in the reactivity are essentially thermodynamic. The activation strain model (ASM) has been used to get more insights into the critical effect of the metal center in these cycloadditions, and the results reveal that the change in reactivity is entirely explained on the basis of the differences in the interaction energies Eint between the cluster and the alkyne. Further decomposition of the Eint values through the localized molecular orbital-energy decomposition analysis (LMO-EDA) indicates that substitution of the Mo atoms in cluster [1](+) by W induces changes in the electronic structure of the cluster that result in weaker intra- and inter-fragment orbital interactions.

Palladium(0)-Catalyzed Methylcyclopropanation of Norbornenes with Vinyl Bromides and Mechanism Study

An unusual methylcyclopropanation from [2 + 1] cycloadditions of vinyl bromides to norbornenes catalyzed by Pd(OAc)2/PPh3 in the presence of CH3ONa and CH3OH has been established. A methylcyclopropane subunit was installed by a 3-fold domino procedure involving a key protonation course. Preliminary deuterium-labeling studies revealed that the proton came from methyl of CH3OH and also exposed an additional hydrogen/deuterium exchange process. These two proton-concerned reactions were fully chemoselective.

An efficient d-glucosamine-based copper catalyst for C–X couplings and its application in the synthesis of nilotinib intermediate

d-Glucosamine has been studied for C–N and C–S bond formations via cross-coupling reactions of nitrogen and sulfur nucleophiles with both aryl iodides and bromides.

Recent advances in C–S bond formation via C–H bond functionalization and decarboxylation

The development of mild and general methods for C–S bond formation has received significant attention because the C–S bond is indispensable in many important biological and pharmaceutical compounds.

Palladium-catalyzed direct ortho-sulfonylation of azobenzenes with arylsulfonyl chlorides via C–H activation

ortho-Sulfonylated azobenzenes were obtained in moderate to high yields by direct ortho-sulfonylation of azobenzenes' C–H bond with arylsulfonyl chlorides.

Generation of ArS-substituted flavone derivatives using aryl thiols as sulfenylating agents

The regioselective and metal-free sulfenylation of flavones was achieved under aerobic conditions with ammonium iodide as an inducer.

Novel glycosyl pyridyl-triazole@palladium nanoparticles: efficient and recoverable catalysts for C–C cross-coupling reactions

A series of glycosyl pyridyl-triazole@palladium nanoparticles have been prepared and applied in efficient C–C coupling such as Suzuki–Miyaura coupling, Heck reaction and Sonogashira reaction.

Piperazinylpyrimidine modified MCM-41 for the ecofriendly synthesis of benzothiazoles by the simple cleavage of disulfide in the presence of molecular O2

Synthesis of benzothiazoles by metal free cleavage of disulfide bond.

Silver-mediated oxidative vinylic C–H bond sulfenylation of enamides with disulfides

A silver-mediated oxidative vinylic C–H bond sulfenylation of enamides was developed. This method is compatible with diaryl and dialkyl disulfides to deliver the biologically precious chalcogenated olefins efficiently. A plausible non-chain radical mechanism was proposed for understanding this novel sulfenylation based on the mechanistic studies.

d-Glucosamine as a green ligand for copper catalyzed synthesis of aryl sulfones from aryl halides and sodium sulfinates

d-Glucosamine is reported for the first time as a green ligand for copper catalyzed coupling of aryl halides and sodium sulfinates, which provides a simple and extremely efficient new route to unsymmetrical diaryl sulfones.