Divergent Synthesis of Allenylsulfonamide and Enaminonesulfonamide via In(III)-Catalyzed Couplings of Propargylamine and N-Fluorobenzenesulfonimide

Assembly of Diverse Allenes via Activator-Free Palladium-Catalyzed Regioselective γ-Arylation of Propargylamines with Boronic Acids

Controlling the reaction selectivity to achieve a precision synthesis is a constant concern for chemists. Here, we report a palladium-catalyzed deaminative coupling of propargylamines with arylboronic acids to generate allene skeletons. Importantly, this approach allows the regioselective γ-arylation of unactivated propargyl tertiary amines to access various allenes in the absence of amino-activating reagents. We present a wide range of propargylamines and boronic acids and demonstrate the synthetic application of the target products to construct valuable compounds.

Electrophilic aromatic substitution of electron-rich arenes with N-fluorobenzenesulfonimide (NFSI) as an electrophile

An efficient amidation of electron-rich arenes using NFSI as a nitrogen source has been successfully disclosed. This amidation process can be easily conducted at elevated temperatures, without the need for catalysts or additives. A wide range of arenes substituted with hydroxy, alkoxy, or carbonyl groups were found to be compatible, yielding the desired amination products. Computational study shows that the amidation proceeds via an electrophilic aromatic substitution pathway, comprising a three-step process that includes substitution, addition, and elimination, which differs slightly from the classical mechanism.

Metal free regio - and stereoselective semireduction of CF3-substituted N-allenamides

We developed a chemoselective metal-free access for the 1,2- and 2,3-semireduction of CF3-N-allenamides. The enamide functionality of CF3-substituted N-allenamides could be efficiently reduced by Et3SiH/BF3·OEt2 in total regioselectivity and good stereoselectivity, whereas DBU promoted the isomerization of the resulting allyl amide leading exclusively to the E-configurated enamide.

Spray-Assisted Interfacial Polymerization to Form CuII/I@CMC-PANI Film: An Efficient Dip Catalyst for A3 Reaction

A novel and interesting method for the preparation of carboxymethylcellulose-polyaniline film-supported copper catalyst (CuII/I@CMC-PANI) has been developed via spray-assisted interfacial polymerization. Using copper sulfate as an initiator, spraying technology was introduced to form a unique interface that is perfectly beneficial to the polymerization of aniline monomers onto carboxymethylcellulose macromolecule chains. To further confirm the composition and structure of the as-prepared hybrid film, it was systematically characterized by inductively coupled plasma (ICP), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and thermogravimetric analysis (TGA) techniques. The Cu content in the fresh CuII/I@CMC-PANI film was determined to be 1.805 mmol/g, and spherical nanoparticles with an average size of ca. 10.04 nm could be observed in the hybrid film. The CuII/I@CMC-PANI hybrid film was exerted as a dip catalyst to catalyze the aldehyde-alkyne-amine (A3) coupling reactions. High yields of the products (up to 97%) were obtained in this catalytic system, and the catalyst could be easily picked up from the reaction mixture by tweezers and reused for at least six consecutive runs, without any discernible losses in its activity in the model reaction. The dip catalyst of CuII/I@CMC-PANI, with easy fabrication, convenient deployment, superior catalytic activity, and great reusability, is expected to be very useful in organic synthesis.

An N-Fluorinated Imide for Practical Catalytic Imidations

Catalytic imidation using NFSI as the nitrogen source has become an emerging tool for oxidative carbon-nitrogen bond formation. However, the less than ideal benzenesulfonimide moiety is incorporated into products, severely detracting its synthetic value. As a solution to this challenge, we report herein the development of a novel N-fluorinated imide, N-fluoro-N-(fluorosulfonyl)carbamate (NFC), by which the attached imide moiety acts as a modular synthetic handle for one-step derivatization to amines, sulfonamides, and sulfamides. Furthermore, this study revealed the superior reactivity of NFC as showcased in a copper-catalyzed imidation of benzene derivatives and imidocyanation of aliphatic alkenes, overcoming the limitation of NFSI-mediated reactions.

Copper-Catalyzed Synthesis of Terminal vs. Fluorine-Substituted N-Allenamides via Addition of Diazo Compounds to Terminal Ynamides

A copper-mediated coupling reaction between ynamides and diazo-compounds to produce N-allenamides is reported for the first time. This method enables facile and rapid access to terminal N-allenamides by using commercially available TMS-diazomethane with wide functional group compatibility on the nitrogen. Furthermore, the ubiquity of molecules containing a fluorine moiety in medicine, in agricultural, and material science requires the continuous search of new building blocks, including this unique surrogate. The CuI/diazo protocol was successfully applied to the synthesis of fluorine-substituted N-allenamides. DFT calculations provided insights in the mechanism involved.

Ligand-free copper-catalyzed C(sp3)-H imidation of aromatic and aliphatic methyl sulfides with N-fluorobenzenesulfonimide

A novel and efficient process has been developed for copper-catalyzed C(sp3)-H direct imidation of methyl sulfides with N-fluorobenzenesulfonimide(NFSI). Without using any ligands, various methyl sulfides including aromatic and aliphatic methyl sulfides, can be transformed to the corresponding N-((phenylthio)methyl)-benzenesulfonamide derivatives in good to excellent yields.

Synthesis of Aminoallenes via Selenium-π-Acid-Catalyzed Cross-Coupling of N-Fluorinated Sulfonimides with Simple Alkynes

The facile synthesis of aminoallenes, accomplished by a selenium-π-acid-catalyzed cross-coupling of an N-fluorinated sulfonimide with simple, non-activated alkynes, is reported. Until now, aminoallenes were difficult to be accessed by customary means, inasmuch as pre-activated and, in part, intricate starting materials were necessary for their synthesis. In sharp contrast, the current study shows that ordinary internal alkynes can serve as simple and readily available precursors for the construction of the aminoallene motif. The operating reaction conditions tolerate numerous functional groups such as esters, nitriles, (silyl)ethers, acetals, and halogen substituents, furnishing the target compounds in up to 86 % yield.

Exploring the behavior of the NFSI reagent as a nitrogen source

The diverse biological activities of nitrogen-containing compounds make the construction of the C-N bond of great importance. As N-fluorobenzenesulfonimide, one of the most abundant chemical feedstock, has a dual behaviour, i.e. as an electrophilic fluorination and amidation source, it attracts the attention of synthetic chemists for exploitation. This review comprehensively summarizes the significant progress of the efficient and mild amidation reactions, with an emphasis on approaches for the generation of nitrogen-centered intermediates, related mechanisms and new synthetic chemistry methods that offer opportunities to overcome obstacles in pharmaceutical applications. In this perspective, we discuss the developments in the amidation reaction using NFSI in the past decade. We discuss the recent progress, challenges and future outcomes in the area of amidation chemistry using commercially available NFSI.