Carbon-nitrogen Double Bond Research Articles

Studies on the interaction of isocyanides with imines: reaction scope and mechanistic variations

The interaction of imines with isocyanides has been studied. The main product results from a sequential process involving the attack of two units of isocyanide, under Lewis acid catalysis, upon the carbon–nitrogen double bond of the imine to form the 4-membered ring system. The scope of the reaction regarding the imine and isocyanide ranges has been determined, and also some mechanistic variations and structural features have been described.

Enantioselective methodologies using N-carbamoyl-imines

Nucleophilic addition to carbon-nitrogen double bonds (imines) represents one of the most common strategies for the synthesis of amine derivatives. In order to circumvent the problem associated with low reactivity of imines in nucleophilic addition, various imines with electron-withdrawing groups at nitrogen have been studied, and many of them were successfully applied in asymmetric methodologies. Especially N-carbamoyl imines were found to be useful in the enantioselective synthesis of various organic compounds, due to their increased reactivity toward nucleophiles as well as limited difficulties connected with the removal of the carbamoyl moiety in target molecules. The aim of this review is to cover enantioselective methods based on N-carbamoyl imines, focusing on synthetically useful protocols.

ChemInform Abstract: Enantioselective Cycloaddition Reactions of Ketenes Catalyzed by N‐Heterocyclic Carbenes

AbstractReview: 94 refs.

ChemInform Abstract: Synthesis of Fluorinated β‐Aminophosphonates and γ‐Lactams.

AbstractComputational studies explain the observed diastereoselectivity of the title synthesis.

Enantioselective Cycloaddition Reactions of Ketenes Catalyzed by N-Heterocyclic Carbenes

This account summarizes recent research in our group on the development of N-heterocyclic carbene (NHC) catalyzed cycloaddition reactions of ketenes. The NHCs were found to be efficient catalysts for the enantioselective [2+2]-, [2+2+2]-, [3+2]-, and [4+2]-cycloaddition reactions of ketenes with various electrophiles, such as imines, carbonyl compounds, oxaziridines, oxodienes and azadienes. The NHC-catalyzed [4+2] cycloaddition of α,β-unsaturated acyl chlorides was also investigated. 1 Introduction 2 [2+2] Cycloaddition of Ketenes 2.1 With Carbon–Nitrogen Double Bonds 2.2 With Carbon–Oxygen Double Bonds 2.3 With Oxygen–Nitrogen and Nitrogen–Nitrogen Double Bonds 2.4 With X=Y=Z Bonds 3 [3+2] Cycloaddition of Ketenes 4 [4+2] Cycloaddition of Ketenes 5 [4+2] Annulation of Unsaturated Acyl Chlorides 6 Conclusions and Outlook

Synthesis of Fluorinated β-Aminophosphonates and γ-Lactams

The functionalized polyfluorophosphorylated 1-azadienes I have been prepared by a Wittig reaction of ethyl glyoxalate and perfluorophosphorylated conjugated phosphoranes, obtained by reaction of phosphazenes and fluorinated acetylenic phosphonates. Subsequent reduction of both carbon-carbon and carbon-nitrogen double bonds of these 1-azadienes I affords the fluorine-containing β-aminophosphonates II, with the syn β-aminophosphonate being obtained as the major diastereoisomer. Base-mediated cyclocondensation of a diastereomeric mixture of aminophosphonates II leads exclusively to a new type of functionalized trans-γ-lactams III in a diastereoselective way. A computational study has also been used to explain the observed diastereoselectivity of these reactions.

ChemInform Abstract: Phosphorus Derivatives of Hydroxylamines, Oximes and Hydroxamic Acids

AbstractReview: 298 refs.

Influence of N2 and H2O on UV Irradiated Bio Polymer Composite

This study reports on the effect of UV-light on the FTIR spectra of bio polymer doped with 10 % TiO2 (BPF1.0) in a gas cell full with nitrogen gas (N2) and a droplet of water (H2O). The film samples were put in the 10 cm NaCl gas cell with 99.99 % N2 with H2O at different exposure time of 40 °C. An unexposed gas cell fill with N2 and H2O is used for the purposed of comparison. The chemical structural changes in the UV irradiated gas cell were monitored by Fourier-transform infrared (FTIR) spectroscopy methods. The changes in hydroxyl, (OH) and carbon nitrogen double bond, (C=N) of bio polymer doped with TiO2 under UV exposures were discussed. OH and C=N intensities decreases of exposed to UV light under N2 with H2O in gas cell. The UV-radiation shows FTIR spectrum changes on BPF1.0 of exposed to nitrogen gas and water.

Synthesis of phthalazinones via palladium(ii)-catalysed intramolecular oxidative C–H/C–H cross-coupling of N′-methylenebenzohydrazides

A palladium(II)-catalysed intramolecular oxidative C-H/C-H cross-coupling of N'-methylenebenzohydrazides to phthalazin-1(2H)-ones has been developed. This cyclization is believed to mechanistically proceed via electrophilic ortho-palladation and subsequent C-arylation of the carbon-nitrogen double bond.

Two Structures of a Thiazolinyl Imine Reductase from Yersinia enterocolitica Provide Insight into Catalysis and Binding to the Nonribosomal Peptide Synthetase Module of HMWP1

The thiazolinyl imine reductase from Yersinia enterocolitica (Irp3) catalyzes the NADPH-dependent reduction of a thiazoline ring in an intermediate for the formation of the siderophore yersiniabactin. Two structures of Irp3 were determined in the apo (1.85 Å) and NADP(+)-bound (2.31 Å) forms. Irp3 is structurally homologous to sugar oxidoreductases such as glucose-fructose oxidoreductase and 1,5-anhydro-d-fructose reductase, as well as to biliverdin reductase. A homology model of the thiazolinyl imine reductase from Pseudomonas aeruginosa (PchG) was generated. Extensive loop insertions are observed in the C-terminal domain that are unique to Irp3 and PchG and not found in the structural homologues that recognize small molecular substrates. These loops are hypothesized to be important for binding of the nonribosomal peptide synthetase modules (found in HMWP1 and PchF, respectively) to which the substrate of the reductase is covalently attached. A catalytic mechanism for the donation of a proton from a general acid (either histidine 101 or tyrosine 128) and the donation of a hydride from C4 of nicotinamide of the NADPH cofactor is proposed for reduction of the carbon-nitrogen double bond of the thiazoline.

ChemInform Abstract: Stereoselective Olefination and Regiospecific Vicinal Difunctionalization of Imines with α‐(Benzothiazol‐2‐ylsulfonyl) Carbonyl Compounds.

Depending on their structures, imines are able to undergo either olefination or vicinal difunctionalization with various α-(benzothiazol-2-ylsulfonyl) carbonyl compounds in the absence of external bases. The olefination reaction of aromatic imines with α-(benzothiazol-2-ylsulfonyl) carbonyl compounds proceeds smoothly in tetrahydrofuran at 70 °C to give structurally diverse α,β-unsaturated esters, amides, and ketones in good to excellent yields and with extremely high (E) selectivity. In contrast, the carbon–nitrogen double bonds of cyclic imines and the carbon–carbon double bonds of α,β-unsaturated imines are subjected to regiospecific vicinal difunctionalization with α-(benzothiazol-2-ylsulfonyl) carbonyl compounds under the same reaction conditions to give a variety of benzothiazole derivatives in good to excellent yields. It is noteworthy that the benzothiazole moiety is present in a number of antitumor agents and bioluminescent molecules. In addition, plausible reaction pathways have been proposed to account for these transformations, and these are substantially supported by ESI-MS analysis of the reaction mixtures.

Linking of amino-capped quinonediimines by divalent transition metal ions: Synthesis, characterization, and comparison to electronic structure calculations

Quantum mechanical density functional theory (DFT) calculations are reported for novel, self-assembled transition metal linked dimers of N,N′-bis (3′-carboxy,4′-aminophenyl)-1,4-quinonediimine, with the metals manganese, iron, cobalt, nickel, copper and zinc each in the +2 oxidation state. Infrared spectroscopy detected systematic changes in the carbon–nitrogen double bond involving the imine nitrogen atoms, from 1457cm−1 for manganese complex to 1622cm−1 for the iron complexes. The calculated electronic band gaps of the complexes compare favorably to those for the uncomplexed quinonediimines. The synthesis of the compounds demonstrates a feasible route to the design of a tunable architecture of linear molecular wires derived from properly derivatized quinonediimines.

Recent Advances in the Asymmetric Synthesis of α-(Trifluoromethyl)-Containing α-Amino Acids

This review article provides a comprehensive update on the development of new methods for the asymmetric synthesis of α-(trifluoromethyl)-α-amino acids, covering the literature from 2006 to mid-February 2012. Most of the methods discussed are based on asymmetric additions across the carbon–nitrogen double bond of the imines derived from esters of 3,3,3-trifluoropyruvic acid. Medium to high levels of stereocontrol can be achieved using phenylglycinol-derived chiral auxiliaries attached to the nitrogen of the corresponding imines. Among the enantioselective approaches, impressive results were achieved through the application of the Strecker­ reaction using chiral thioureas, as well as chiral Bronsted acids, as organocatalysts. 1 Introduction 2 Stoichiometric Asymmetric Syntheses of α-(Trifluoromethyl)-α-amino Acids 3 Catalytic Asymmetric Syntheses of α-(Trifluoromethyl)-α-amino Acids 4 Miscellaneous 5 Conclusions

Stereoselective Olefination and Regiospecific Vicinal Difunctionalization of Imines with α‐(Benzothiazol‐2‐ylsulfonyl) Carbonyl Compounds

AbstractDepending on their structures, imines are able to undergo either olefination or vicinal difunctionalization with various α‐(benzothiazol‐2‐ylsulfonyl) carbonyl compounds in the absence of external bases. The olefination reaction of aromatic imines with α‐(benzothiazol‐2‐ylsulfonyl) carbonyl compounds proceeds smoothly in tetrahydrofuran at 70 °C to give structurally diverse α,β‐unsaturated esters, amides, and ketones in good to excellent yields and with extremely high (E) selectivity. In contrast, the carbon–nitrogen double bonds of cyclic imines and the carbon–carbon double bonds of α,β‐unsaturated imines are subjected to regiospecific vicinal difunctionalization with α‐(benzothiazol‐2‐ylsulfonyl) carbonyl compounds under the same reaction conditions to give a variety of benzothiazole derivatives in good to excellent yields. It is noteworthy that the benzothiazole moiety is present in a number of antitumor agents and bioluminescent molecules. In addition, plausible reaction pathways have been proposed to account for these transformations, and these are substantially supported by ESI‐MS analysis of the reaction mixtures.

Synthesis, Spectroscopic Characterization, and In Vitro Antimicrobial Studies of Pyridine-2-Carboxylic Acid N′-(4-Chloro-Benzoyl)-Hydrazide and Its Co(II), Ni(II), and Cu(II) Complexes

N-substituted pyridine hydrazide (pyridine-2-carbonyl chloride and 4-chloro-benzoic acid hydrazide) undergoes hydrazide formation of the iminic carbon nitrogen double bond through its reaction with cobalt(II), nickel(II), and copper(II) metal salts in ethanol which are reported and characterized based on elemental analyses, IR, solid reflectance, magnetic moment, molar conductance, and thermal analysis (TG). From the elemental analyses data, 1 : 2 metal complexes are formed having the general formulae [MCl2(HL)2] ·yH2O (where M = Co(II), Ni(II), and Cu(II), y = 1–3). The important infrared (IR) spectral bands corresponding to the active groups in the ligand and the solid complexes under investigation were studied. IR spectra show that ligand is coordinated to the metal ions in a neutral bidentate manner with ON donor sites. The solid complexes have been synthesized and studied by thermogravimetric analysis. All the metal chelates are found to be nonelectrolytes. From the magnetic and solid reflectance spectra, the complexes (cobalt(II), nickel(II), and copper(II)) have octahedral and square planner geometry, respectively. The antibacterial and antifungal activity's data show that the metal complexes have a promising biological activity comparable with the parent ligand against bacterial and fungal species.

New insights into the mechanism of the Schiff base hydrolysis catalyzed by type I dehydroquinate dehydratase from S. enterica: a theoretical study

The reaction pathway of Schiff base hydrolysis catalyzed by type I dehydroquinate dehydratase (DHQD) from S. enterica has been studied by performing molecular dynamics (MD) simulations and density functional theory (DFT) calculations and the corresponding potential energy profile has also been identified. On the basis of the results, the catalytic hydrolysis process for the wild-type enzyme consists of three major reaction steps, including nucleophilic attack on the carbon atom involved in the carbon-nitrogen double bond of the Schiff base intermediate by a water molecule, deprotonation of the His143 residue, and dissociation between the product and the Lys170 residue of the enzyme. The remarkable difference between this and the previously proposed reaction mechanism is that the second step here, absent in the previously proposed reaction mechanism, plays an important role in facilitating the reaction through a key proton transfer by the His143 residue, resulting in a lower energy barrier. Comparison with our recently reported results on the Schiff base formation and dehydration processes clearly shows that the Schiff base hydrolysis is rate-determining in the overall reaction catalyzed by type I DHQD, consistent with the experimental prediction, and the calculated energy barrier of ∼16.0 kcal mol(-1) is in good agreement with the experimentally derived activation free energy of ∼14.3 kcal mol(-1). When the imidazole group of His143 residue is missing, the Schiff base hydrolysis is initiated by a hydroxide ion in the solution, rather than a water molecule, and both the reaction mechanism and the kinetics of Schiff base hydrolysis have been remarkably changed, clearly elucidating the catalytic role of the His143 residue in the reaction. The new mechanistic insights obtained here will be valuable for the rational design of high-activity inhibitors of type I DHQD as non-toxic antimicrobials, anti-fungals, and herbicides.

Cyclic Imines: Chemistry and Mechanism of Action: A Review

In recent years, there has been an increase in the production of shellfish and in global demand for seafood as nutritious and healthy food. Unfortunately, a significant number of incidences of shellfish poisoning occur worldwide, and microalgae that produce phycotoxins are responsible for most of these. Phycotoxins include several groups of small to medium sized natural products with molecular masses ranging from 300 to over 3000 Da. Cyclic imines (CIs) are a recently discovered group of marine biotoxins characterized by their fast acting toxicity, inducing a characteristic rapid death in the intraperitoneal mouse bioassay. These toxins are macrocyclic compounds with imine (carbon-nitrogen double bond) and spiro-linked ether moieties. They are grouped together due to the imino group functioning as their common pharmacore and due to the similarities in their intraperitoneal toxicity in mice. Spirolides (SPXs) are the largest group of CIs cyclic imines that together with gymnodimines (GYMs) are best characterized. Although the amount of cyclic imines in shellfish is not regulated and these substances have not been categorically linked to human intoxication, they trigger high intraperitoneal toxicity in rodents. In this review, the corresponding chemical structures of each member of the CIs and their derivatives are reviewed as well as all the data accumulated on their mechanism of action at cellular level.

ChemInform Abstract: Homo‐ and Heterogeneous Organocatalysis: Enantioselective Mannich Addition of Ketones to Endocyclic Carbon—Nitrogen Double Bonds.

Abstract The proline-catalyzed Mannich addition of ketones to chalkogenazines is reported. Yields and enantioselectivities of the corresponding products were good to excellent, using different types of organocatalysts. Furthermore the immobilization of hydroxyproline into a readily synthesized polystyrene-copolymer was accomplished. The catalytic performance of this heterogeneous catalyst was successfully demonstrated in the discussed Mannich reaction.

Synthetically useful carbon–carbon and carbon–sulphur bond construction mediated by carbon- and sulphur-centred radicals in water and aqueous media

This account is focused on carbon–carbon, and carbon–sulphur bond-forming reactions through the use of carbon- and sulphur-centred radicals in water, respectively. It intends to show the scope and applications of these types of radicals with a synthetic goal, thus helping the radical synthetic chemist to grasp the fundamental aspects of the syntheses of a wide array of organic compounds through radical methods in environmentally friendly media. This account excludes the syntheses of organic substrates with the aid of organometallic/metal-centred radicals such as other Group IV-radicals and transition-metal radicals, and the important class of radical reductions currently accomplished in water using different metallic reducing species. The array of substrates synthesized through the present method encompasses intermolecular and intramolecular radical carbon–carbon bond formation reactions in water, and radical carbon–sulphur bond formation reactions. Among the radical carbon–carbon bond formation reactions, special attention is devoted to atom-transfer radical reactions, radical addition reactions to olefins, radical addition to carbon–nitrogen double bonds, the carboaminohydroxylation of alkenes, and the analogues of Knovonoegel reactions, the synthesis of functionalized enol ethers, thr carboazidation and azidation, and ynol formation, and radical cyclization reactions in water.

ChemInform Abstract: Aziridinyl Anions: Generation, Reactivity, and Use in Modern Synthetic Chemistry

AbstractReview: 178 refs.