Desired Amides Research Articles

Phenalenyl-ruthenium synergism for effectual catalytic transformations of primary amines to amides.

The synthesis of amides holds great promise owing to their impeccable contributions as building blocks for highly valued functional derivatives. Herein, we disclose the design, synthesis and crystal structure of a mixed-ligand ruthenium(II) complex, [Ru(η6-Cym)(O,O-PLY)Cl], (1) where Cym = 1-isopropyl-4-methyl-benzene and O,O-PLY = deprotonated form of 9-hydroxy phenalenone (HO,O-PLY). The complex catalyzes the aerobic oxidation of various primary amines (RCH2NH2) to value-added amides (RCONH2) with excellent selectivity and efficiency under relatively mild conditions with common organic functional group tolerance. Structural, electrochemical, spectroscopic, and computational studies substantiate that the synergism between the redox-active ruthenium and π-Lewis acidic PLY moieties facilitate the catalytic oxidation of amines to amides. Additionally, the isolation and characterization of key intermediates during catalysis confirm two successive dehydrogenation steps leading to nitrile, which subsequently transform to the desired amide through hydration. The present synthetic approach is also extended to substitution-dependent tuning at PLY to tune the electronic nature of 1 and to assess substituent-mediated catalytic performance. The effect of substitution at the PLY moiety (5th position) leads to structural isomers, which were further evaluated for the catalytic transformations of amine to amides under similar reaction conditions.

Exploration of Oxidative Ritter-Type Reaction of α-Arylketones and Its Application for the Collective Total Syntheses of Erythrina Alkaloids

Exploration of Oxidative Ritter-Type Reaction of α-Arylketones and Its Application for the Collective Total Syntheses of <i>Erythrina</i> Alkaloids

A Practical Approach for the Transamidation of N,N-Dimethyl Amides with Primary Amines Promoted by Sodium tert-Butoxide under Solvent-Free Conditions

AbstractA practical sodium tert-butoxide (NaOtBu)-mediated protocol is disclosed for the transamidation of various N,N-dimethyl amides with primary amines to afford the corresponding amides in moderate to good yields at room temperature under solvent-free conditions. This protocol features a facile work-up procedure and good functional group compatibility, especially for N,N-dimethyl amides with long-chain alkyl groups and heteroatom-containing amines. Notably, a few representative gram-scale reactions proceed smoothly to furnish the desired amides in high yields, which demonstrates the potential of this process for further practical applications. Several control experiments are carried out and a plausible mechanism is provided.

Development of Triazinone-Based Condensing Reagents for Amide Formation

Novel triazinone-based condensing reagents have been developed. The palladium-catalyzed O-N allylic rearrangement of 2-(allyloxy)-4,6-dichloro-1,3,5-triazine and subsequent regioselective substitution using alcohols and an amine afforded chlorotriazinones, which can be readily converted using N-methylmorpholine into the corresponding condensing reagents. The condensation of carboxylic acids and amines using these reagents proceeded to afford the desired amides in good yields. In comparison with 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride, the newly synthesized triazinone-based condensing reagents exhibited higher reactivity.

Synthesis of Novel α-amidino Carboxylic Acids and their Use as H-Bond Catalysts in Strecker Reaction.

A wide variety of synthesized amidine derivatives are bioactive compounds. They show a vast range of medical properties. Therefore, a simple route for synthesis of novel class of amidine derivatives called amidino carboxylic acids and their use as catalysts in Strecker reaction has been reported in the current work. The stability, local charge density and hydrogen bond parameters were calculated for eight derivatives with different substituents. In order to synthesize these amidino carboxylic acids, we initially prepared Knovenogel condensation products via the reaction of isatin derivatives with malonitrile. When the reaction was performed in water, the resulting nitrile groups of malonitrile derivatives was hydrolyzed with HOAC/ H2SO4 to generate the desired amide groups. The amide groups in resulting compound converted to amine groups with two Hoffman rearrangements in the presence of NaOH/Br2. Further neutralization led to the final zwitterionic α-amidino carboxylic acids. In the next step, the catalytic activity of these compounds as H-bond donor catalyst was investigated in Strecker reaction. The overall yields of the derivatives with substituent on the aromatic ring of starting isatins are higher than that for the overall yields of nitrogen-substituted isatins. The reaction of 5-nitro isatin with the next reagent gives lower yield in aryl-substituted products. An increase of catalytic activity is observed by rising the electron-withdrawing power of the aromatic ring substituents., The presence of nitro group in the structure of catalyst caused a large increase of catalytic activity in Strecker reaction. DFT calculations at B3LYP/6-31++g(d,p) and Lanl2dz level of theory showed that these compounds act as single H-bond catalysts and higher yields were obtained for complexes with stronger hydrogen bond. A simple and efficient method for synthesis of ɑ-amidino carboxylic acids was developed in this research. These compounds have been used as a single H-bond donor catalyst in the Strecker reaction. DFT calculations were carried out to confirm the experimental results. The obtained data from computations are in good agreement with experimental results.

Synthesis of cinnamic amide derivatives and their anti-melanogenic effect in α-MSH-stimulated B16F10 melanoma cells

Of the three enzymes that regulate the biosynthesis of melanin, tyrosinase and its related proteins TYRP-1 and TYRP-2, tyrosinase is the most important because of its ability to limit the rate of melanin production in melanocytes. For treating skin pigmentation disorders caused by an excess of melanin, the inhibition of tyrosinase enzyme is by far the most established strategy. Cinnamic acid is a safe natural product with an (E)-β-phenyl-α,β-unsaturated carbonyl motif that we have previously shown to play an important role in high tyrosinase inhibition. Since cinnamic acid is relatively hydrophilic, which hinders its absorption on the skin, fifteen less hydrophilic cinnamic amide derivatives (1–15) were designed as safe and more potent tyrosinase inhibitors and were synthesized through a Horner-Wadsworth-Emmons reaction. The use of conc-HCl and acetic acid for debenzylation of the O-benzyl-protected cinnamic amides 40–54 produced the following three results. 1) Cinnamic amides 43, 48, and 53 with a 2,4-dibenzyloxyphenyl group, irrespective of the amine type of the amides, produced complex compounds with high polarity. 2) Cinnamic amides 40–42, 44, 50–52, and 54 with a benzylamino, or diethylamino group produced the desired debenzylated cinnamic amides 1–3, 5, 10–13, and 15. 3) Cinnamic amides 45–47, and 49 with an anilino moiety provided 3,4-dihydroquinolinones 16–19 through intramolecular Michael addition of the anilide group. Notably, the use of BBr3 as an alternative debenzylating agent for debenzylation of cinnamic amides 45–49 with the anilino moiety provided our desired cinnamic amides 6–10 without inducing the intramolecular Michael addition. Debenzylation of cinnamic amides 43, 48, and 53 with a 2,4-dibenzyloxyphenyl group was also successfully accomplished using BBr3 to give 4, 9, and 14. Among the nine compounds that inhibited mushroom tyrosinase more potently at 25 μM than kojic acid, four cinnamic amides 4, 5, 9, and 14 showed 3-fold greater tyrosinase inhibitory activity than kojic acid. The docking simulation using tyrosinase indicated that these four cinnamic amides (−6.2 to −7.9 kcal/mol) bind to the active site of tyrosinase with stronger binding affinity than kojic acid (−5.7 kcal/mol). All four cinnamic amides inhibited melanogenesis and tyrosinase activity more potently than kojic acid in α-MSH-stimulated B16F10 melanoma cells in a dose-dependent manner without cytotoxicity. The strong correlation between tyrosinase activity and melanin content suggests that the anti-melanogenic effect of cinnamic amides is due to tyrosinase inhibitory activity. Considering that the cinnamic amides 4, 9, and 14, which exhibited strong inhibition on mushroom tyrosinase and potent anti-melanogenic effect in B16F10 cells, commonly have a 2,4-dihydroxyphenyl substituent, the 2,4-dihydroxyphenyl substituent appears to be essential for high anti-melanogenesis. These results support the potential of these four cinnamic amides as novel and potent tyrosinase inhibitors for use as therapeutic agents with safe skin-lightening efficiency.

One-Pot Regioselective and Stereoselective Synthesis of C-Glycosyl Amides from Glycals Using Vinyl Azides as Glycosyl Acceptors.

The reaction of glycals containing good leaving groups with aromatic vinyl azides to give α- C-glycosyl amides in good yields is described. Various vinyl azides with different groups undergo the reaction smoothly. In these reactions, an iminodiazonium intermediate is generated by the attack of the vinyl azide onto the glycal under Lewis acid conditions. This undergoes Schmidt-type denitrogenative 1,2-migration to form a nitrilium ion, which, upon hydrolysis, gives the desired C-glycosyl amide.

Novel 6- and 7-Substituted Coumarins with Inhibitory Action against Lipoxygenase and Tumor-Associated Carbonic Anhydrase IX.

A series of carboxamide derivatives of 6- and 7-substituted coumarins have been prepared by an original procedure starting from the corresponding 6- or 7-hydroxycoumarins which were alkylated with ethyl iodoacetate, and the obtained ester was converted to the corresponding carboxylic acids which were thereafter reacted with a series of aromatic/aliphatic/heterocyclic amines leading to the desired amides. The new derivatives were investigated as inhibitors of two enzymes, human carbonic anhydrases (hCAs) and soy bean lipoxygenase (LOX). Compounds 4a and 4b were potent LOX inhibitors, whereas many effective hCA IX inhibitors (KIs in the range of 30.2–30.5 nM) were detected in this study. Two compounds, 4b and 5b, showed the phenomenon of dual inhibition. Furthermore, these coumarins did not significantly inhibit the widespread cytosolic isoforms hCA I and II, whereas they were weak hCA IV inhibitors, making them hCA IX-selective inhibitors. As hCA IX and LOX are validated antitumor targets, these results are promising for the investigation of novel drug targets involved in tumorigenesis.

DEAD‐Promoted Oxidative Ugi‐Type Reaction Including an Unprecedented Ugi Amidation Assisted by Dicarboxylic Acids

A mild and metal‐free DEAD‐promoted (DEAD = diethyl azodicarboxylate) oxidative Ugi‐type reaction of tertiary amines has been demonstrated. The reaction gives easy access to α‐amino amides and imides with diverse functional groups in good isolated yields. This Ugi‐type approach achieves an unprecedented synthesis of α‐amino amide analogues with the assistance of dicarboxylic acids, and not water, for the introduction of the carbonyl oxygen atom of the amide moiety. Mechanistic studies indicated that the dicarboxylic acids may readily undergo an intramolecular annulation, instead of the Mumm rearrangement, to give the desired amide with one molecule of anhydride released.

Pd/C-Catalyzed Aminocarbonylation of Aryl Iodides with Anthranils in Water Using Mo(CO)6 as the CO Source.

A convenient procedure for the synthesis of N-(2-carbonylaryl)benzamides has been developed. Through Pd/C-catalyzed aminocarbonylation of anthranils with various hindered and functionalized aryl iodides, the desired amides were afforded in moderate to good yields. The protocol is advantageous due to the recyclable Pd/C catalyst, safe Mo(CO)6 as the solid CO source, and environmentally benign water as solvent. No inert atmosphere protection is needed.

One-Pot Amide Bond Formation from Aldehydes and Amines via a Photoorganocatalytic Activation of Aldehydes.

A mild, one-pot, and environmentally friendly synthesis of amides from aldehydes and amines is described. Initially, a photoorganocatalytic reaction of aldehydes with di-isopropyl azodicarboxylate leads to an intermediate carbonyl imide, which can react with a variety of amines to afford the desired amides. The initial visible light-mediated activation of a variety of monosubstituted or disubstituted aldehydes is usually fast, occurring in a few hours. Following the photocatalytic reaction, addition of the primary amine at room temperature or the secondary amine at elevated temperatures leads to the corresponding amide from moderate to excellent yields without epimerization. This methodology was applied in the synthesis of Moclobemide, a drug against depression and social anxiety.

Formation of Amides from Imines via Cyanide-Mediated Metal-Free Aerobic Oxidation.

A new protocol for the direct formation of amides from imines derived from aromatic aldehydes via metal-free aerobic oxidation in the presence of cyanide is described. This protocol was applicable to various aldimines, and the desired amides were obtained in moderate to good yields. Mechanistic studies suggested that this aerobic oxidative amidation might proceed via the addition of cyanide to imines followed by proton transfer from carbon to nitrogen in the original imines, leading to carbanions of α-amino nitriles, which undergo subsequent oxidation with molecular oxygen in air to provide the desired amide compounds.

An efficient, green and scale-up synthesis of amides from esters and amines catalyzed by Ru-MACHO catalyst under mild conditions

An efficient, green and scale-up synthesis of amides from esters and amines has been developed using Ru-MACHO as a readily available catalyst. A diverse range of amides were obtained in moderate to excellent yields (55–98%). Furthermore, when the scale of the amidation reaction was increased to 240.0mmol, the desired amide still could be obtained in high yield (48.2g of N-benzylbenzamide, 95%).

ChemInform Abstract: Palladium‐Catalyzed Carbonylative Synthesis of N‐(2‐Cyanoaryl)benzamides and Sequential Synthesis of Quinazolinones.

A convenient procedure for the synthesis of N-(2-cyanoaryl)benzamides has been developed. Using aryl bromides and 2-aminobenzonitriles as the substrates, Mo(CO)6 as the CO source, the desired amides were produced in good yields. Quinazolinones were produced in good yields in a sequential manner as well.

Palladium-catalyzed carbonylative synthesis of N-(2-cyanoaryl)benzamides and sequential synthesis of quinazolinones

A convenient procedure for the synthesis of N-(2-cyanoaryl)benzamides has been developed. Using aryl bromides and 2-aminobenzonitriles as the substrates, Mo(CO)6 as the CO source, the desired amides were produced in good yields. Quinazolinones were produced in good yields in a sequential manner as well.

Facile preparation of amides from carboxylic acids and amines with ion-supported Ph3P

Ion-supported Ph3P, 4-(diphenylphosphino)benzyltrimethylammonium bromide (IS-Ph3P), could be used for the facile amidation of a wide range of carboxylic acids with amines in the presence of bromotrichloromethane to provide the corresponding amides in good yields. In the present reaction, the desired amides were obtained in good yields with high purity by simple extraction of the reaction mixture with diethyl ether or chloroform and subsequent removal of the solvent from the extract. Moreover, ion-supported Ph3PO (IS-Ph3PO), which was a co-product derived from IS-Ph3P in the present reductive condensation, was recovered in high yield and could be reduced to IS-Ph3P for reuse in the same amidation of carboxylic acid.

Mechanism of arylboronic acid-catalyzed amidation reaction between carboxylic acids and amines

Arylboronic acids were found to be efficient catalysts for the amidation reactions between carboxylic acids and amines. Theoretical calculations have been carried out to investigate the mechanism of this catalytic process. It is found that the formation of the acyloxyboronic acid intermediates from the carboxylic acid and the arylboronic acid is kinetically facile but thermodynamically unfavorable. Removal of water (as experimentally accomplished by using molecular sieves) is therefore essential for overall transformation. Subsequently C-N bond formation between the acyloxyboronic acid intermediates and the amine occurs readily to generate the desired amide product. The cleavage of the C-O bond of the tetracoordinate acyl boronate intermediates is the rate-determining step in this process. Our analysis indicates that the mono(acyloxy)boronic acid is the key intermediate. The high catalytic activity of ortho-iodophenylboronic acid is attributed to the steric effect as well as the orbital interaction between the iodine atom and the boron atom.

A traceless approach to amide and peptide construction from thioacids and dithiocarbamate-terminal amines

A novel and traceless strategy has been devised that allows a coupling of thioacids and dithiocarbamate-terminal amines. This strategy had been assumed to be dependent on the attachment of a functional equivalent of a cysteine side chain in earlier native chemical ligation approaches. This approach enables the traceless removal of CS2 to directly generate the desired amide bond and is compatible with a range of unprotected side chains of amino acid. The ability to produce amide or peptides by a traceless removal of the auxiliary is a significant virtue of the method. Meanwhile, the application of this new peptide-bond-forming reaction to the synthesis of novel endomorphin (EM) derivatives with various binding potencies was realized.

ChemInform Abstract: Pd‐Catalyzed One‐Pot Chemoselective Hydrogenation Protocol for the Preparation of Carboxamides Directly from Azides.

AbstractSuccinimide esters are subjected to the reaction with azides under conditions A) to give the desired amides within a short time in good yields.

Isoform-specific Prolongation of Kv7 (KCNQ) Potassium Channel Opening Mediated by New Molecular Determinants for Drug-Channel Interactions

Kv7 channels, especially Kv7.2 (KCNQ2) and Kv7.3 (KCNQ3), are key determinants for membrane excitability in the brain. Some chemical modulators of KCNQ channels are in development for use as anti-epileptic drugs, such as retigabine (D-23129, N-(2-amino-4-(4-fluorobenzylamino)-phenyl)), which was recently approved for clinical use. In addition, several other compounds were also reported to potentiate activity of the Kv7 channels. It is therefore of interest to investigate compound-channel interactions, so that more insights may be gained to aid future development of therapeutics. We have conducted a screen of 20,000 compounds for KCNQ2 potentiators using rubidium flux combined with atomic absorption spectrometry. Here, we report the characterization of a series of new structures that display isoform specificity and induce a marked reduction of deactivation distinct from that of retigabine. Furthermore, KCNQ2(W236L), a previously reported mutation that abolishes sensitivity to retigabine, remains fully sensitive to these compounds. This result, together with mutagenesis and other studies, suggests that the reported compounds confer a unique mode of action and involve new molecular determinants on the channel protein, consistent with the idea of recognizing a new site on channel protein.