Stereoselective reactions. XXXII. Enantioselective deprotonation of 4-tert-butylcyclohexanone by fluorine-containing chiral lithium amides derived from 1-phenylethylamine and 1-(1-naphthyl)ethylamine

Enantioselective deprotonation of 4-tert-butylcyclohexanone was examined using 1-phenylethylamine- and 1-(1-naphthyl)ethylamine-derived chiral lithium amides having an alkyl or a fluoroalkyl substituent at the amide nitrogen. The lithium amides having a 2,2,2-trifluoroethyl group on the amide nitrogen are easily accessible in both enantiomeric forms, and were found to induce good enantioselectivity in the present reaction.     

Interaction of the Azole N‐Sodium Derivatives with Freon‐113: Synthesis of N‐(2,2‐dichlorotrifluoroethyl)azoles

The synthesis of 2,2‐dichlorotrifluoromethyl derivatives of azoles and diphenylamine by the interaction of N‐sodium salts with Freon‐113 has been carried out. The sodium salts of heterocycles, having a one‐ring nitrogen atom, react with Freon‐113 without catalysis. The sodium salts of heterocycles, having two‐ or three‐ring nitrogen atoms, react with Freon‐113 in the presence of tetrabutylammonium iodide as a catalyst.     

Ultramicrodetermination of nitrogen in organic compounds: Centimilligram determination of nitrogen with sealed tube method

A new improved nitrometer was developed for centimilligram determination of nitrogen by the sealed-tube method. A combustion tube having an internal volume of 1 ml was used and the sample was weighted in a boat made of copper foil, which was made by a simple device. The accurate volume of a gas granule of the blank was evaluated by observation with a micrometer microscope. A standard deviation of 0.240% was rapidly and conveniently obtained with organic compounds having a range of 5.94–66.4% nitrogen.     

Stereodivergent approaches to the synthesis of isoxazolidine analogues of alpha-amino acid nucleosides. Total synthesis of isoxazolidinyl deoxypolyoxin C and uracil polyoxin C

The synthesis of new nucleoside analogues is currently of high interest. We report here full details of a study leading to the synthesis of novel isoxazolidinyl analogues of alpha-amino acid nucleosides. Three different synthetic approaches starting from L-serine have been evaluated for the construction of the isoxazolidine ring. These approaches consisted of Michael addition of N-benzylhydroxylamine to alpha,beta-unsaturated esters, nucleophilic addition of silyl ketene acetals to nitrones and 1, 3-dipolar cycloaddition of nitrones with vinyl acetate. Both Michael addition and nucleophilic addition of enolates could be carried out with stereocontrol at the newly formed stereogenic carbon. The stereocontrol observed in these reactions arises from the protecting group arrangement in the L-serine-derived substrates. Thus, whereas compounds having a diprotected nitrogen led to syn adducts, compounds having a monoprotected nitrogen gave rise to anti adducts. On the other hand, substrates having either a diprotected or monoprotected nitrogen atom led to anti adducts through the cycloaddition route. So, by choosing the appropriate route, isoxazolidinyl analogues having either syn or anti configuration with respect to the glycine unit can be prepared in enantiomerically pure form. The stereoselective synthesis of isoxazolidinyl analogues of deoxypolyoxin C and uracil polyoxin C in both D and L enantiomeric forms using these techniques has been achieved in good yields.     

Solid-phase synthesis of isoquinolinones using Bischler-Napieralski cyclization

Isoquinolinone is a structural unit found in many natural products having various important biological activities. A traceless solid-phase synthetic approach has been developed to prepare isoquinolinone derivatives. This approach enables one to synthesize isoquinolinones having various moieties on benzene nuclei and also can produce derivatives with a proton on the amide nitrogen.     

First-principles Study on Neutral Nitrogen Impurities in Zinc Oxide

The atomic geometries, electronic structures, and formation energies of neutral nitrogen im-purities in ZnO have been investigated by first-principles calculations. The nitrogen impuri-ties are always deep acceptors, thus having no contributions to p-type conductivity. Among all the neutral nitrogen impurities, nitrogen substituting on an oxygen site has the lowest formation energy and the shallowest acceptor level, while nitrogen substituting on a zinc site has the second-lowest formation energy in oxygen-rich conditions. Nitrogen interstitials are unstable at the tetrahedral site and spontaneously relax into a kick-out configuration. Though nitrogen may occupy the octahedral site, the concentrations will be low for the high formation energy. The charge density distributions in various doping cases are discussed, and self-consistent results are obtained.     

Polymerization induced by electron-beam irradiation of octadecyl methacrylate in the form of a multilayer or monolayer

In continuation of the previous series of studies, polymerization of octadecyl methacrylate (ODMA) induced by electron beams has been investigated in a form of its multilayer or monolayer in an attempt to prepare a stable thin polymer film having a regular layer structure. ODMA multilayers were prepared by the Langmuir-Blodgett technique and irradiated with electron beams from a Van de Graaff accelerator. Multiple reflection infrared spectroscopy and x-ray diffractometry revealed that the ODMA multilayer was polymerized to give a thin polymer film having a regular layered structure when irradiated in nitrogen atmosphere, but no indication of polymerization was observed when irradiated in air. A preliminary study on the ODMA monolayer at a nitrogen–water interface indicated that the monolayer was polymerized.     

Synthesis of Biologically Important N‐Heteroaryl‐2‐(heteroarylthio)acetamides

The synthesis of compounds having triazole and selena/thiadiazole rings connected by a chain having sulfur and nitrogen in the link has been described. The resultant N‐heteroaryl‐2‐(heteroarylthio)acetamide may be biologically important as related compounds found application in the inhibition of HIV 1 replications.     

Novel synthesis of lactam from alkyne having amide in a tether using fischer chromium carbene complex

A novel lactam synthesis from alkyne having amide in a tether was developed. The reaction proceeds via a vinylketene complex generated from alkyne and Fischer chromium carbene complex, and the lactam ring was formed from carbon monoxide, alkyne carbon and nitrogen of tosylamide. The four-,five-, six-, and seven-membered lactams having a substituent at the -position were obtained in good yields.     

Electronic and steric control in regioselective addition reactions of organolithium reagents with enaldimines

A reaction mode of imines derived from naphthalene-1-carbaldehyde and acyclic alpha,beta-unsaturated aldehydes with organolitium reagents was dependent on the characteristic nature of a substituent on the imine nitrogen atom. An imine having an electron-withdrawing aryl group on the nitrogen atom behaves as a 1,2-directing imine toward organolithium reagents. In contrast, an imine bearing an alkyl or a bulky aryl group favors 1,4-addition of organolithium reagents. Electronic and steric tuning of a substituent on the imine nitrogen atom for a reaction mode was rationalized on the basis of molecular orbital calculations.     

Synthesis of Fused Quinolizine Derivatives by Condensation of Cyclic Schiff Bases with β-Keto Esters

A new procedure has been developed for the synthesis of fused nitrogen-containing heterocycles having a bridgehead nitrogen atom via condensation of cyclic Schiff bases with β-keto esters.     

Influence of nitrogen speciation on the TDN measurement in fresh waters by high temperature catalytic oxidation and persulfate digestion

Analytical methodologies for the determination of total dissolved nitrogen (TDN) in waters are based on a conversion step able to transform selectively all the nitrogen species into a compound that is then quantified. A crucial requirement to meet accuracy is the quantitative recovery of all organic and inorganic nitrogen species during the conversion step. In this work, the N recoveries of two widely employed methodologies that use different conversion steps (high temperature catalytic oxidation (HTCO) and persulfate digestion (PD)) were assessed on a set of organic nitrogen compounds, representative of the structures of both dissolved organic matter (DOM) and anthropogenic contaminants. Low recoveries are due to poor selectivity during the conversion step, with the formation of nitrogen compounds other than nitrogen oxide (HTCO) and nitrate (PD). The results show that in many instances the TDN measurements give systematically low results depending on N speciation. PD could give lower results than HTCO even for samples containing only DOM of biological origin. In particular (i) low N recovery was always observed with compounds having two or more contiguous N atoms; (ii) the HTCO method is very effective for TDN quantification in the presence of s-triazine rings while PD method did not yield satisfactory N recovery; (iii) a full N recovery was observed with compounds having amido or amino groups or nitrogen atoms in imidazole, indole and pyrimidine rings; and (iv) the N recoveries for purine derivatives are almost complete with HTCO, but give systematically low results by PD.

Finally, the estimation of dissolved organic nitrogen (DON) fluxes and pools from TDN measurements can be affected by uncertainties larger than previously thought as a consequence of (i) the lower N recovery for some nitrogen compounds and (ii) the differences in the N recovery as a function of the adopted analytical methods.     

Palladium(0)-catalyzed synthesis of medium-sized heterocycles by using bromoallenes as an allyl dication equivalent

We have developed a highly regio- and stereoselective synthesis of medium-sized heterocycles containing one or two heteroatoms via cyclization of bromoallenes bearing an oxygen, nitrogen, or carbon nucleophilic functionality in the presence of a palladium(0) catalyst and alcohol. In this reaction, bromoallenes act as an allyl dication equivalent, and the intramolecular nucleophilic attack takes place exclusively at the central carbon atom of the allene moiety. Interestingly, bromoallenes having a carbon nucleophile with a five-atom tether afford eight-membered rings with trans-configuration, while those having an oxygen or a nitrogen nucleophile give the corresponding cis-rings selectively. This is the first example that demonstrates the synthesis of medium-sized rings via cyclization of bromoallenes, and this reaction provides a very useful method for a catalytic synthesis of seven- and eight-membered heterocycles without using high dilution conditions.     

Total synthesis of (±)-erythrocarine using dienyne metathesis

Total Synthesis of (±)-erythrocarine was achieved using ruthenium-catalyzed dienyne metathesis as a key step. A tetrahydroisoquinoline skeleton having tetrasubstituted carbon center was constructed using our method, that is, carbon dioxide and an alkyl group were introduced onto an alkyne having a heteroatom in a tether using the nickel complex to produce α,β-unsaturated carboxylic acid and then isoquinoline skeleton was constructed by Michael reaction of the tethered nitrogen to the resultant α,β-unsaturated ester.     

Adsorbent of Noble Metals,Based on Copolymers of Divinyl Sulfide and 4-Vinylpyridine

Russian Journal of Applied Chemistry - Radical copolymerization of divinyl sulfide and 4-vinylpyridine was used to synthesize 3D copolymers having in their structure “pyridine” nitrogen...     

Synthesis of mesoporous zeolite a by resorcinol-formaldehyde aerogel templating

Mesoporous zeolite A has been synthesized by using a template method with resorcinol-formaldehyde aerogels having three-dimensional mesopores. It was characterized with X-ray powder diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, field emission scanning electron microscopy, thermogravimetric analysis, and nitrogen adsorption/desorption. The pore size distribution calculated from the nitrogen adsorption isotherm is a bimodal distribution with micropores and mesopores. Field emission scanning electron micrograph observations confirm the presence of mesopores.     

Obtention de complexes du platine(II) du type [PtCl2(amine)L] par rupture des dimeres pontes [Pt2Cl4(amine)2]

Opening of chlorine-bridged amine dimers of platinum(II) by various ligands L yields quantitatively complexes of general formula [PtCl₂(amine)L] with a cis configuration in most cases. Cis olefinic complexes may be easily obtained by this method, together with compounds having L as a weak ligand. For the reactions of two-sites ligandsd (nitrogen—olefin), the determining factor seems to be correlated to the nucleophilicity of the binding site; platinum always coordinates at the nitrogen atom of the nitrogen unsaturated ligands which have been studied.     

Nitrogen-doped carbon aerogel synthesis by solvothermal gelation for supercapacitor application

Journal of Solid State Electrochemistry - Nitrogen-doped mesoporous carbon aerogel having high surface area and high nitrogen content was synthesized by sol–gel method for supercapacitor...     

Ring-cleavage of isoxazoles with heterocyclic amines. Synthesis of fused pyrimidines

The reaction between 2-substituted ethyl 2,5-dihydro-5-oxoisoxazole-4-carboxylates ( 2a,b ) and heterocyclic amines 1, 4 , and 6 , having the amino group in position 2 with respect to the nuclear nitrogen afforded fused pyrimidines 3, 5 , and 7 .     

Crystal structure of (1,10-phenanthroline-N,N')(1,4,7,10-tetraazacyclododecane-N,N',N",N"')nickel(II) diperchlorate.

The crystal structure of the title compound, [Ni(C8H20N4)(C12H8N2)](ClO4)2, has been determined by X-ray diffraction. The Ni(II) ion is six coordinated with four nitrogen atoms of the tetradentate macrocyclic ligand and two nitrogen atoms of the bidentate ligand in a distorted octahedron geometry. The folded tetradentate macrocyclic ligand adopts a configuration having four five-membered chelate rings in distorted eclipsed conformations. The four hydrogen atoms of the amine groups of the macrocyclic ligand are on the same side towards the bidentate ligand.