Efficient copper-catalyzed N-arylation of sulfoximines with aryl iodides and aryl bromides

Thermal Nickel-Catalyzed N-Arylation of NH-Sulfoximines with (Hetero)aryl Chlorides Enabled by PhPAd-DalPhos Ligation

We report a versatile method for cross-coupling of NH-sulfoximines with (hetero)aryl chlorides, as well as bromide and sulfonate electrophiles, that makes use of the air-stable, commercial precatalyst (PhPAd-DalPhos)Ni(o-tol)Cl. Under optimized conditions a diverse electrophile scope is established, including the N-arylation of the pharmaceutical Clozapine. While 5 mol % Ni and 80 °C are commonly employed in this chemistry, successful examples utilizing 1 mol % Ni and/or 25 °C are presented. Competition experiments establish the superiority of NH-sulfoximine over primary sulfonamide as nucleophiles under these conditions.

A New Rapid and Specific Iodination Reagent for Phenolic Compounds

A new rapid iodination reagent, N1,N3,N5-tris[(2,4,6-trimethylpyridine)iodo(I)]-2,4,6-triphenyl-s-triazine trihexafluorophosphate, was synthesized in a modification of the established synthesis of 2,4,6-triiodo-3,5-dimethylphenol in the presence of bis(2,4,6-trimethylpyridine)iodo(I) hexafluorophosphate and used for the precise post-modification of mono- and trisubstituted phenyl compounds. We performed triple iodinations with our new phenyl-based compounds as a proof of principle of selected types of phenols, ß-sympatholytic agents and their spin-labeled derivatives, which can be employed in electron paramagnetic resonance (EPR) spectroscopy. The new rapid iodination reagent can be employed with high reactivity and regioselectivity.

Decarboxylative sulfoximination of benzoic acids enabled by photoinduced ligand-to-copper charge transfer

Sulfoximines are synthetically important scaffolds and serve important roles in drug discovery. Currently, there is no solution to decarboxylative sulfoximination of benzoic acids; although thoroughly investigated, limited substrate scope and harsh reaction conditions still hold back traditional thermal aromatic decarboxylative functionalization. Herein, we realize the first decarboxylative sulfoximination of benzoic acids via photo-induced ligand to copper charge transfer (copper-LMCT)-enabled decarboxylative carbometalation. The transformation proceeds under mild reaction conditions, has a broad substrate scope, and can be applied to late-stage functionalization of complex small molecules.

Photo-catalyzed acetoxysulfoximination of styrene with sulfoximidoyl thianthrenium salt

We report the design and synthesis of a redox-active thianthrenium-containing sulfoximination reagent. Photo-catalyzed acetoxysulfoximination of styrene with various functional groups is described. Preliminary mechanistic studies indicated that the sulfoximination reagent (2aa) received a single electron transfer (SET) from the photo-excited Ir(ppy)₃ catalyst to produce a sulfoximidoyl radical as a key intermediate in this transformation.

Visible-Light-Induced N-Acylation of Sulfoximines

A metal-, base-, and additive-free N-acylation of sulfoximines was developed under mild conditions using organic photoredox catalyst. This green strategy featured broad substrate scope, good compatibility with air, and high yields (up to 96%). It could be further applied to amino acid modifications and α-keto N-acyl sulfoximine synthesis without any complicated transformations or operations.

Lewis acid triggered N-alkylation of sulfoximines through nucleophilic ring-opening of donor-acceptor cyclopropanes: synthesis of γ-sulfoximino malonic diesters

Scandium triflate (Sc(OTf)₃) catalyzed, mild, and regioselective ring-opening reaction of donor-acceptor (D-A) cyclopropanes has been developed using sulfoximines for the synthesis of γ-sulfoximino malonic diesters. This protocol allows the synthesis of different N-alkyl sulfoximines in good to excellent yields (up to 94%) with broad functional group tolerance. In this process, N-H and C-C bonds are cleaved to form new C-N and C-H bonds. The feasibility of this method is supported by a gram-scale reaction and synthetic elaboration of the obtained product.

Electrochemical Oxidative C(sp3)-H/N-H Coupling of Diarylmethanes with Sulfoximines or Benzophenone Imine

Herein, we report an efficient electrochemical method for the synthesis of N-alkylated sulfoximines by electrochemical oxidative C(sp³)-H/N-H coupling of sulfoximines and diarylmethanes. In addition, we used the same conditions for electrochemical dehydrogenative amination of diarylmethanes with benzophenone imine as an aminating agent. The reactions showed good functional group tolerance and afforded the corresponding products in moderate to good yields without the use of a stoichiometric oxidant, a metal catalyst, or an activating agent.

Chiral Polythiophenes: Part I: Syntheses of Monomeric Precursors

The purpose of this mini-review is to comprehensively present the synthetic approaches used for the preparation of non-racemic mono- and multi-substituted thiophenes, which, in turn, can be applied as precursors for the synthesis of chiral polythiophenes isolated as a single chemical entity or having supramolecular thin-layer architectures.

Pd-Catalyzed double carbopalladation/syn-insertion cascade reactions toward medium-size sulfoximine heterocycles

With the assistance of Ac in sulfoximine as a protecting group (PG) and MeOH as a de-PG agent, Pd-catalyzed multicomponent reactions were developed to access indene-fused medium-size sulfoximine heterocycles. The reactions proceeded smoothly under exceptionally mild conditions to produce polyheterocyclic sulfoximines with regiospecificity and good functional group tolerance. A double carbopalladation/syn-insertion of triple bond sequences was proposed tothis transformation.

Nickel-Catalyzed N-Arylation of NH-Sulfoximines with Aryl Halides via Paired Electrolysis

A novel strategy for the N-arylation of NH-sulfoximines has been developed by merging nickel catalysis and electrochemistry (in an undivided cell), thereby providing a practical method for the construction of sulfoximine derivatives. Paired electrolysis is employed in this protocol, so a sacrificial anode is not required. Owing to the mild reaction conditions, excellent functional group tolerance and yield are achieved. A preliminary mechanistic study indicates that the anodic oxidation of a Ni^II species is crucial to promote the reductive elimination of a C-N bond from the resulting Ni^III species at room temperature.

Chiral polymers based on thiophenes functionalized at the 3-position with a pendant containing a stereogenic sulfur atom. Synthetic and structural aspects

The first synthesis of new, chiral polythiophenes functionalized at the 3-position of the thiophene ring with a pendant containing a stereogenic sulfur atom of sulfoxides, sulfoximines or sulfinates was developed.

N-Arylation of NH-Sulfoximines via Dual Nickel Photocatalysis

The pharmaceutically underexplored sulfoximine moiety has emerged as a potentially active pharmaceutical ingredient. We developed a scalable synthetic route to N-arylated sulfoximines from the respective “free” NH-sulfoximines and bromoarenes. Our strategy is based on a dual nickel photocatalytic approach, is applicable for a broad scope of substrates, and exhibits a highly functional group tolerance. In addition, we could demonstrate that other sulfoximidoyl derivatives like sulfonimidamides and sulfinamides proceed smoothly under the developed reaction conditions.

Construction of N-S and C-N Bonds from Reactions of Benzofuroxans with DMSO or THF

Novel ring-opening reactions are achieved employing benzofuroxan as a new type of iminating or aminating reagent. These diverse transformations give access to three types of molecular scaffolds, N-aryl dimethylsulfoximines, methanesulfonamides, and hemiaminal ethers, which are important structural motifs in organic and medicinal chemistry. The procedures feature solvent-involved reactions, easily available starting materials, operational simplicity, high atom economy, and the potential further transformation of nitro group.

Visible-Light-Mediated Photoredox-Catalyzed N-Arylation of NH-Sulfoximines with Electron-Rich Arenes

The direct C-H/N-H dehydrogenative cross-coupling of NH-sulfoximines with electron-rich arenes was realized by oxidative visible-light photoredox catalysis, applying 9-mesityl-10-methylacridinium perchlorate as an organic photocatalyst. Sulfoximines display diverse desirable properties for medicinal chemistry and the pharmaceutical industry. However, their preparation is still challenging. Our reaction proceeds without sacrificial oxidant, at room temperature and is highly selective for the C-N bond forming reaction. The scope of the reaction includes mono- and multi-alkylated and halogenated arenes, which are reacted with aromatic and aliphatic electron-rich and electron-poor NH-sulfoximines, giving moderate to excellent yields of the N-arylated sulfoximines. In addition, we successfully conducted the developed reaction on a gram scale (1.5 g). Mechanistic investigations show that both arene and NH-sulfoximine interact with the excited-state of the photocatalyst. We propose a radical-based mechanism, where both the arene and the NH-sulfoximine are photo-oxidized to their respective radical intermediates. Radical-radical cross-coupling subsequently leads to the N-arylated sulfoximine. Two electrons and two protons are released during the reaction and are subsequently converted into H2 by a proton-reducing cobalt-catalyst.

Palladium-Catalyzed N-Arylation of Sulfoximines with Aryl Sulfonates

Palladium-catalyzed C-N bond coupling reaction between NH-sulfoximines and aryl halides (e.g., -Br, -I, and -Cl and pseudohalides -OTf and -ONf) was successfully achieved. Nevertheless, aryl tosylates/mesylates left much to be achieved. In this report, a general N-arylation of sulfoximines with aryl sulfonates is described. Using Pd(OAc)₂/MeO-CM-phos complex, the N-aryl sulfoximine products can be obtained in good-to-excellent yields (up to 99%) with good common functional group compatibility. In addition to arene moieties, alkenyl tosylates are shown to be successful coupling partners.

Copper-catalyzed oxidative decarboxylative coupling of α-keto acids and sulfoximines

The formation of N-aroylsulfoximines via a copper-catalyzed oxidative decarboxylative coupling of α-keto acids with NH-sulfoximines is reported.

Metal-Free, Phosphonium Salt-Mediated Sulfoximination of Azine N-Oxides: Approach for the Synthesis of N-Azine Sulfoximines

Herein, we report a simple and metal-free method for the synthesis of N-azine sulfoximines by the nucleophilic substitution of azine N-oxides with NH-sulfoximines. The present method works at room temperature with wide functional group compatibility and gives several unprecedented N-azine sulfoximines. The reaction conditions were also found suitable with enantiopure substrates and furnished products without any racemization. It also finds an application in the sulfoximination of azine-based functional molecules such as 2,2'-bipyridine, 1,10-phenanthroline, and quinine.

Palladium nanoparticles catalyzed aroylation of NH-sulfoximines with aryl iodides

A novel approach towards aroylation of NH-sulfoximines with aryl iodides in the presence of carbon monoxide using Pd nanoparticles stabilized by a binaphthyl backbone (Pd-BNP) has been developed.

Expanding the structure-activity relationship of sulfoxaflor: the synthesis and biological activity of N-heterocyclic sulfoximines

BACKGROUND

Sulfoxaflor, a new insect control agent developed by Dow AgroSciences, exhibits broad-spectrum control of many sap-feeding insect pests, including aphids, whiteflies, leafhoppers, planthoppers and lygus bugs. During the development of sulfoxaflor, structure-activity relationship (SAR) exploration of the sulfoximine functional group revealed that the nature of the sulfoximine nitrogen substituent significantly affects insecticidal acitivity. As part of the investigation to probe the various electronic, steric and lipophilic parameters at this position, a series of N-heterocyclic sulfoximines were synthesized and tested for bioactivity against green peach aphid.

RESULTS

Using a variety of chemistries, the nitrile substituent was replaced with different substituted five- and six-membered heterocycles. The compounds in the series were then tested for insecticidal acitivty against green peach aphid in foliar spray assays. In spite of the larger steric demand of these substituents, the resulting N-heterocyclic sulfoximine analogs displayed good levels of efficacy. In particular, the N-thiazolyl sulfoximines exhibited the greatest activity, with LC50 values as low as 1 ppm.

CONCLUSIONS

The novel series of N-heterocyclic sulfoximines helped to advance the current knowledge of the sulfoxaflor SAR, and demonstrated that the structural requirement for the sulfoximine nitrogen position was not limited to small, electron-deficient moeities, but rather was tolerant of larger functionality.