Synthesis of Amides via the Amination of Aldehydes with Hydroxylamines Promoted by TBAF·3H2O

A metal-free, mild, and efficient method for the synthesis of amides has been developed from the amination of aldehydes with hydroxylamines promoted by TBAF·3H2O in the presence of KOH. Control experiments showed that the nitrone was the intermediate of this amination. By this method, a series of amides, biologically active compounds bebenil and a COX inhibitor were obtained in moderate to good yields.

Exploring the Versatility of the Amidation of Aryl Acid Fluorides using the Germylamines R3 GeNMe2

The formation of amide bonds is an important process since this linkage is an essential component in proteins, pharmaceuticals, and other medicinally and biologically significant molecules. Recently, it was demonstrated that germylamines R3 GeNR'2 were useful reagents for the conversion of acid fluorides to amides. This transformation occurs readily at room temperature and has a low activation energy. In the present study, the versatility of this amidation reaction with aryl acid fluorides is investigated. A series of thirteen acid fluorides with various substituents on the aromatic ring were reacted with the germylamine Ph3 GeNMe2 and twelve of these were converted to the corresponding amides in high yields, the exception being 1,4-benzenedicarbonyl difluoride. The germylamines Bun 3 GeNMe2 and Pri 3 GeNMe2 also could be used for this interconversion, and both of these species successfully converted 1,4-benzenedicarbonyl difluoride to the corresponding amide. In addition, the crystal structure of Ph3 GeNMe2 is reported. This represents one of only three crystallographically characterized germylamines. The synthesis and 19 F NMR characterization of three fluorogermanes R3 GeF (R=Bun , Pri , and Mes) are also reported herein.

KOH-promoted cascade C-Cl bond activation and amidation of trichloromethyl aromatic compounds with formamides in water

A KOH-promoted cascade C-Cl bond activation and amidation of trichloromethyl aromatic compounds with formamides using water as a solvent has been developed. This methodology suggested an alternative synthetic approach for the synthesis of aryl amide compounds in the absence of catalysts, additives and organic solvents. In addition, the yields of gram-scale reactions are good and provide a basis for synthetic application.

A convenient synthesis of N-(hetero)arylamides by the oxidative coupling of methylheteroarenes with amines

An oxidative amidation of 2-methylpyridines/2-methylbenzimidazole with amines using copper acetate and elemental sulfur in DMSO to afford various N-(hetero)arylamides has been accomplished. Mechanistic studies reveal the intermediacy of N-(pyridin-2-ylmethyl)aniline and confirm the role of DMSO as the oxygen source.

The Reaction of Ketoximes with Hypervalent Iodine Reagents: Beckmann Rearrangement and Hydrolysis to Ketones

We investigated the reaction of ketoximes with hypervalent iodine reagents. A combination of PhI(OAc)2 and BF3·Et2O promoted the Beckmann rearrangement of ketoximes, thus yielding the corresponding amides. From a detailed investigation of the reaction, we determined that the Beckmann rearrangement is preceded by acetylation of the hydroxy group of the ketoxime in situ, accelerating the Beckmann rearrangement. We confirmed that the acetylated ketoxime undergoes the Beckmann rearrangement with BF3·Et2O. The reaction of ketoximes with Koser’s reagent [PhI(OH)OTs] in the presence of tetrahydrofuran results in hydrolysis, affording the corresponding ketones in high yields at room temperature.

Tandem oxidative amidation of benzylic alcohols by copper(II) supported on metformin-graphitic carbon nitride nanosheets as an efficient catalyst

In this research, an efficient heterogeneous catalyst based on graphitic carbon nitride nanosheets (CN) has been reported. The CN was functionalized by 1,3-dibromopropane as a linker (CN–Pr–Br) and subsequently modified with metformin (CN–Pr–Met). Furthermore, the copper(II) was coordinated on modified CN (CN–Pr–Met–Cu(II)) and during this process, 7.94% copper(II) was loaded into the catalyst structure. The synthesized catalyst was evaluated by various techniques including fourier-transform infrared spectroscopy (FT-IR), energy dispersive X-ray spectroscopy (EDS), field emission scanning electron microscopy (FE-SEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and inductively coupled plasma atomic emission spectroscopy (ICP-OES). CN–Pr–Met–Cu(II) was used as a catalyst in the synthesis of amides via the oxidation of benzyl alcohols. The conditions of this reaction were optimized in terms of temperature, time, amount of catalyst, type of base, oxidant, and solvent. Moreover, a variety of amides with an efficiency of 75–95% were synthesized. The reaction was carried out in the presence of benzyl alcohols, amine hydrochloride salts, tert-butyl hydroperoxide (TBHP), CaCO₃, and CN–Pr–Met–Cu(II) at 80 °C of acetonitrile solvent. The synthesized catalyst can be easily separated from the reaction medium and reused for 7 consecutive runs without a significant reduction in reaction efficiency.

Copper(II)-β-cyclodextrin immobilized on graphitic carbon nitride nanosheets as a highly effective catalyst for tandem oxidative amidation of benzylic alcohols

In this study, an efficient catalyst based on graphitic carbon nitride nanosheets (CN) and copper(II) supported β-cyclodextrin (β-CD/Cu(II)) was synthesized and used for tandem oxidative amidation of benzylic alcohols. In this regard, CN was functionalized by β-CD/Cu(II) via 1,3-dibromopropane linker (CN-Pr-β-CD/Cu(II)). The prepared catalyst was characterized using FT-IR, XRD, FE-SEM, EDS, TGA, ICP-OES, BET, and TEM analyses. CN-Pr-β-CD/Cu(II) was subsequently applied in a direct oxidative amidation reaction and it was observed that different benzyl alcohols were converted to desire amides with good to excellent efficiency. This reaction was performed in the presence of amine hydrochloride salts, tert-butyl hydroperoxide (TBHP), and Ca₂CO₃ in acetonitrile (CH₃CN) under nitrogen atmosphere. CN-Pr-β-CD/Cu(II) can be recycled and reused five times without significant reduction in reaction efficiency.

Palladium-Catalyzed Desulfurative Hiyama Coupling of Thioureas to Achieve Amides via Selective C–N Bond Cleavage

Palladium-catalyzed Hiyama coupling of active thioureas via selective C–N bond cleavage is reported. Notably, the new approach employed active thioureas as coupling partners in the presence of arylsilanes to give amides in good yield. Further, this strategy, which utilized CuF2 as a key oxidant and activator, afforded various amide products under mild conditions and an easy to handle procedure without extra base.

Redox-Neutral Dehydrogenative Cross-Coupling of Alcohols and Amines Enabled by Nickel Catalysis

Presented herein is a facile and straightforward synthetic method for the construction of amides via Ni/NHC-catalyzed amidation of alcohols with amines. The strategy exhibits various advantages over existing methods, including...

Visible-light-mediated amidation from carboxylic acids and tertiary amines via C-N cleavage

In this communication, we report a photocatalyzed amidation strategy from carboxylic acids and tertiary amines through the C-N bond cleavage. A wide scope of structurally diverse carboxylic acids participates smoothly...

Aerobic oxidation of primary amines to amides catalyzed by an annulated mesoionic carbene (MIC) stabilized Ru complex

A Ru complex, stabilized by an annulated mesoionic carbene ligand, catalyzes the aerobic oxidation of a host of primary amines to amides in high yields and excellent selectivity. Kinetics, Hammett and DFT studies provide mechanistic insight.

Synthesis of Titanium Complexes Supported by Carbinolamide- and Amide-Containing Ligands Derived from Ti(NMe2)4-Mediated Selective Amidations of Carbonyl Groups

An efficient strategy for the syntheses of a series of titanium complexes has been developed. This protocol features the employment of Ti(NMe₂)₄ both as the metal center to trigger the deprotonation of the ligands and as an amine source to proceed the amidation reactions of carbonyl functionalities of the ligands. Treatment of Ti(NMe₂)₄ with a ligand HL1 (HL1 = 2,2'-(((2-hydroxybenzyl)azanediyl)bis(ethane-2,1-diyl))bis(isoindoline-1,3-dione) results in the formation of Ti(L1')(NMe₂) (1) (H₃L1' = N1-(2-((2-(1-(dimethylamino)-1-hydroxy-3-oxoisoindolin-2-yl)ethyl)(2-hydroxybenzyl)amino)ethyl)-N2,N2-dimethylphthalamide). One important feature regarding the synthesis of 1 is the occurrence of the in situ metal-ligand reaction between Ti(NMe₂)₄ and HL1, leading to the simultaneous formations of carbinolamide and amide scaffolds. Another prominent feature in terms of the preparation of 1 is the achievement of the selective ring-opening reaction of one of the two phthalimide units of the HL1 ligand, affording carbinolamide and amide functionalities within one ligand set. The developed methodology characterizes an ample substrate scope. The selective amidation reactions of the carbonyl groups have been realized for a series of analogous ligands HL2-HL7. Density functional theory calculations were employed to disclose the mechanisms for the formation of 1-7, and the details for the selective ring-opening reactions of the phthalimide unit were uncovered.

Fast Amide Couplings in Water: Extraction, Column Chromatography, and Crystallization Not Required

In the micelle of PS-750-M, the presence of 3° amides from the surfactant proline linker mimics dimethylformamide, dimethylacetamide, and N-methyl-2-pyrrolidone. The resultant micellar properties enable extremely fast amide couplings mediated by 1-ethyl-3-(3-(dimethylamino)propyl)carbodiimide (without hydroxybenzotriazole), rather than expensive and specialized coupling agents. Conditions have been developed wherein products precipitate, and isolation by filtration completely avoids the use of organic solvent. This methodology is scalable and avoids product epimerization.

CuCl/TMEDA/nor-AZADO-catalyzed aerobic oxidative acylation of amides with alcohols to produce imides

Although aerobic oxidative acylation of amides with alcohols would be a good complement to classical synthetic methods for imides (e.g., acylation of amides with activated forms of carboxylic acids), to date, there have been no reports on oxidative acylation to produce imides. In this study, we successfully developed, for the first time, an efficient method for the synthesis of imides through aerobic oxidative acylation of amides with alcohols by employing a CuCl/TMEDA/nor-AZADO catalyst system (TMEDA = teramethylethylendiamine; nor-AZADO = 9-azanoradamantane N-oxyl). The proposed acylation proceeds through the following sequential reactions: aerobic oxidation of alcohols to aldehydes, nucleophilic addition of amides to the aldehydes to form hemiamidal intermediates, and aerobic oxidation of the hemiamidal intermediates to give the corresponding imides. This catalytic system utilizes O2 as the terminal oxidant and produces water as the sole by-product. An important point for realizing this efficient acylation system is the utilization of a TMEDA ligand, which, to the best of our knowledge, has not been employed in previously reported Cu/ligand/N-oxyl systems. Based on experimental evidence, we consider that plausible roles of TMEDA involve the promotion of both hemiamidal oxidation and regeneration of an active CuII-OH species from a CuI species. Here promotion of hemiamidal oxidation is particularly important. Employing the proposed system, various types of structurally diverse imides could be synthesized from various combinations of alcohols and amides, and gram-scale acylation was also successful. In addition, the proposed system was further applicable to the synthesis of α-ketocarbonyl compounds (i.e., α-ketoimides, α-ketoamides, and α-ketoesters) from 1,2-diols and nucleophiles (i.e., amides, amines, and alcohols).

DNA metallization: principles, methods, structures, and applications

This review summarizes the research activities on DNA metallization since the concept was first proposed in 1998, covering the principles, methods, structures, and applications.