N,O-heterocyclics13;-14conversion of isoxazolidines into α,β enones

Substituted isoxazolidines formed by 1,3-dipolar cycloaddition of nitrones to alkenes undergo ring-opening elimination to α,β-enones when treated with trimethyl phosphate. The reaction involves initial alkylation giving the isoxazolidinium intermediate which collapses to the α,β-enone by a Hofmann-like elimination having an orientation controlled by electronic factors, the first step being rate-determining.     

Photopolymerization V. Unsensitized solution photocyclopolymerization of N,N ′-alkylenebismaleimides

The term, “photopolymerization,” is defined as a polymerization process in which every chain-propagating step involves a photo-chemical reaction. This type of polymerization is exemplified by the unsensitized solution photocyclopolymerization of several N,N ′-alkylenebismaleimides, substituted at the double bond. N,N ′-Alkylenebismaleimides substituted with a bromine atom or two methyl groups at their double bond produce high polymeric products upon ultraviolet irradiation in solution. A general reaction scheme for the photopolymerization is proposed. Kinetic measurements show that the solution photopolymerization of substituted bismaleimides is a multistep reaction.     

Cycloaddition von Heterocumulenen an CN-Bindungssysteme. 1. Mitteilung. Perhydro-s-triazindione und Perhydro-s-triazinyl-harnstoffe aus N,N,N′-trisubstituieten Formamidinen und Isocyanaten

The addition of methyl isocyanate to N,N-dimethyl-N′-arylformamidines 4d – 4r leads to the perhydro-s-triazine-diones 5d – 5o and to the s-triazinylureas 10a – 10k . The mechanism of formation is discussed. The addition of the arylisocyanates 18a – 18p to the N,N,N′-trialkylformamidines 9 and 27a – 27i furnishes the expected 1,4-cycloaddition products 26 and 27 in good yields. The N,N-di-isopropyl-N′-alkylformamidines 27j – 271 , however, do not undergo 1,4-dipolar cycloadditions and react with the arylisocyanate 18b to yield the alkyl isocyanates 31a – 31c and N,N-diisopropyl-N′-(p-chlorphenyl)-formamidine 32 exclusively.     

Reaction of ketenes with N,N-Disubstituted 2-Aminomethylenecycloalkanones III. Synthesis of N,N-Disubstituted 3,3-Diehloro-4-amino-5,6-polymethylene-3,4-dihydro-α-pyrones

The reaction of dichloroketene with N,N-Disubstituted 2-aminomethylenecyclopentanones, cyclohexanones, cycloheptanones and cyclooctanones gave the 1,4-cycloadducts, namely N,N-Disubstituted 3,3-dichloro-4-amino-5,6-polymethylene-3,4-dihydro-α-pyrones. The structures of these products were determined by uv, ir and nmr spectral data, as well as by dehydrochlorination of the adduct, 3,3-dichloro-4-diphenylamino-5,6-tetramethylene-3,4-dihydro-α-pyrone, which led to 3-chloro-4-diphenylamino-5,6-tetramethylene-α-pyrone. The by-product of the cycloaddition reaction was the N,N-Disubstituted dichloroacetamide, the formation of which varies according to the substituents on the nitrogen atom.     

Bromination of N,N'-Substituted Malonodiamides

Aiming at preparation of biologically active compounds a bromination of N,N'-substituted malonodiamides in a glacial acetic acid was carried out. The use of one equiv of bromine provided monobromo derivatives, with two equiv of bromine dibromo-substituted products were obtained. Among the N,N'-dibenzylamides of alkylmalonic acids only the methyl homolog underwent bromination. The structure of compounds was proved by IR and ¹H NMR spectroscopy. The effect of the compounds synthesized on the central nervous system was investigated.     

Chemistry of Urea Nitro Derivatives: IV. Reaction of N,N'-Dinitrourea with Formaldehyde

Reaction of N,N'-dinitrourea with formaldehyde, depending on the conditions, leads to formation of various hydroxymethyl derivatives of N-nitroamines and products of their further transformations.     

N,Se-Acetals: Preparation and use in diastereoselective radical reactions

A new facile synthesis of N,S- and N,Se-acetals starting from aldehydes and primary amines is presented (Schemes 3–5). These acetals are used as precursors for stereoselective radical deuteration and allylation reactions (Schemes 6 and 7, Tables 1 and 2). The stereochemical outcome of the reactions depends on the radical trap and the substituents at the N-atom. Deuterations give always anti products with moderate to high selectivities. The allylation reactions give either syn or anti products with low to moderate selectivities. The observed stereoselectivities can be explained with a model based on minimization of A^1,3 strain and are controlled by steric and stereoelectronic effects.     

N,N'-Bis(3-triethoxysilyl)phthalic Diamide, N,N'-Bis(3-triethoxysilyl)malonic Damide and Derivatives

Condensation of 3-triethoxysilylpropylamine with malonic amide was studied. The condensation products, dicarboxylic acid diamides (malonic and phthalic), were used for peretherification with triethanolamine and thus new representatives of silatran series compounds were prepared: N,N'-bis(3-triethoxysilyl)malonic diamide and -phthalic diamide. By hydrolytic polycondensation of N,N'-bis(3-triethoxysilyl)malonic diamide we synthesized an organosilicon polymer with silsesquioxane structure, which we studied as a sorbent of platinum group metals rhodium, palladium and platinum. Peculiar features of sorption activity of the polymer and speculative mechanism of metal sorption are discussed.     

Studies on the photochemical oxidation of N,N-diacyl-1,4-dihydropyrazine derivatives

The photochemical oxidation of N,N-diacyl-1,4-dihydropyrazines was investigated by irradiation from a medium-pressure mercury lamp. The main products of the photooxygenation were isolated and unambiguously confirmed by ¹H NMR spectra, ¹³C NMR spectra, H-H, C-H correlation spectra, high-resolution mass spectrometry, and single-crystal x-ray diffraction analysis. The complicated NMR spectra of main products were studied by variable-temperature NMR experiments. The mechanism of the photooxygenation of N,N-diacyl-1,4-dihydropyrazines is suggested to be a [2 + 2] cycloaddition of oxygen to the double bond.     

Synthesis of 4,5-dihydrothiazole derivatives by the reaction of perfluoro-2-methylpent-2-en-3-yl isothiocyanate with ambident N,O- and N,S-nucleophiles

The reactions of perfluoro-2-methylpent-2-en-3-yl isothiocyanate with ambident N,O- and N,S-nucleophiles (thiazole-2-thione, pyridine-2-thione, 2-hydroxypyridine, benzothiazole-2-thione, benzoxazole-2-thione, 3,4,5,6-tetrahydropyrimidine-2-thione) in the presence of triethylamine yield only 2-N-substituted 4,5-dihydrothiazole derivatives. The molecular structures of three products were determined by X-ray diffraction analysis. The reaction pathways are discussed.     

Synthesis of Five-Membered N,N,N- and N,N,N,N-Heterocyclic Compounds: Applications of Microwaves

The development of new strategies for the synthesis of small-sized heterocycles has remained a highly attractive but challenging proposition. An overview of the application of microwave irradiation to the synthesis of five-membered heterocyclic compounds containing three and four nitrogen atoms is presented, focusing on the developments in the past 5–10 years. This contribution covers the literature concerning the total synthesis of N,N,N- and N,N,N,N-heterocycles. The literature data are summarized based on the size and type of cycles.     

N,N′-Bis(2-hydroxybenzyl)ethylenediamine-N,N′-dipropionic acid. A new chelating ligand for iron(III)

A new potentially chelating ligandN,N′-bis(2-hydroxybenzyl)ethylenediamine-N,N′-dipropionic acid, (HBEP) has been prepared in high yield and its ionization constants have been determined by potentiometric and spectrophotometric methods. The stability constant for the Fe^III-HBEP chelate has been determined spectrophotometrically, and the ligational behaviour of HBEP with iron(III) compared with that of its homologue, HBED (N,N′-bis(2-hydroxybenzyl)ethylenediamine-N,N′-diacetic acid). IPCL Communication No. 169.     

Reaction of N,N-Dialkylcarboxamides with Halogens

N,N-Dialkylcarboxamides react with halogens in the absence of water to form complexes which are likely to have an ionic structure with the Hlg⁺ ion coordinated at the carbonyl oxygen atom. These products can be isolated as individual compounds. Complexes with bromine undergo further transformations to afford bis-dialkylamide hydrogen tribromide and the corresponding -bromo amide. When the reaction is carried out in the presence of water, the products are only bis-dialkylamide hydrogen tribromides; here, the N-alkyl groups act as a source of protons.     

Stable N,N’-Diarylated Dihydrodiazaacene Radical Cations

Three stable N,N’-diarylated dihydroazaacene radical cations were prepared by oxidation of neutral N,N’-diarylated dihydroazaacenes synthesized via palladium-catalyzed Buchwald-Hartwig aminations of aryl iodides with N,N’-dihydroazaacenes. Both neutral as well as oxidized species were investigated via UV-vis spectroscopy, single crystal analysis, and DFT calculations. All the radical cations are surprisingly stable—their absorption spectra in dichloromethane remain unchanged in ambient conditions for at least 24 hours.     

<Emphasis Type="Italic">peri</Emphasis>-Naphthylenediamines: XXXIX. Synthesis and Structure of <Emphasis Type="Italic">N,N′,N′</Emphasis>-Trimethyl-<Emphasis Type="Italic">N</Emphasis>-nitrosonaphthalene-1,8-diamine Derivatives

The corresponding N-nitroso derivatives were synthesized by the action of nitrous acid on N,N,N′-trimethylnaphthalene-1,8-diamine, N,N,N′-trimethyl-5-nitronaphthalene-1,8-diamine, and N,N,N′-trimethylacenaphthene-5,6-diamine, and molecular structure of the products was studied.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 7, 2005, pp. 1020–1027.Original Russian Text Copyright © 2005 by Koroleva, Dyablo, Pozharskii, Sennikova, Starikova.     

Reaction of 4-(N,N-Dimethylaminophenyl)magnesium Bromide with Palladium Tetrakis(triphenylphosphine)

The influence of reaction conditions on catalyzed by Pd(PPh₃)₄ cross-coupling of 4-N,N-dimethylaminophenylmagnesium bromide with 4-bromobenzonitrile in tetrahydrofuran was investigated. The yield of the product of the catalytic process, 4-N,N-dimethylamino-4'-cyanobiphenyl, and of the main product of noncatalytic process, 4-N,N-dimethylaminophenyl 4'-bromophenyl ketone, is mainly governed by the order of introduction of reagents and catalyst into the reaction zone. Experimental observations and analysis of side products suggested conclusions on the processes resulting in deactivation of the catalyst.     

Pyrimidines. 7. A study of the chlorination of pyrimidines with phosphorus oxychloride in the presence of N,N-dimethylaniline

The chlorination of 6-trifluoromethyluracils by phosphorus oxychloride in the presence of N,N-dimethylaniline was studied and compared with results obtained with 6-methyluracils. 6-Trifluoromethyluracil and its 5-chloro analog afforded moderate yields of the di- and trichloropyrimidines, accompanied by good yields of the 2-N-methylanilino by-products, after a 3-hour reaction time. After 24 hours, the 2-N-methylanilinopyrimidines were the primary or sole products. A small yield of 2,4-bis(N-methylanilino)-6-trifluoromethylpyrimidine was also obtained. The 6-methyluracils afforded high yields of the di- and trichloropyrimidines, after 3 and 24 hours, along with minor amounts of the 2-N-methylanilino by-products. After 48 hours, the proportion of 2,4-dichloro-6-methylpyrimidine decreased, and the 2-N-methylanilino product increased. 2-Chloro-4-methylanilino-6-methylpyrimidine and bis(2-N-methylanilino)-6-methylpyrimidine were also formed in small amounts. The chlorination products from 5-chloro-6-methyluracil remained constant over 188 hours of reaction time. It appears that the π electron distribution around the ring, as influenced by the substituents, controls the course of the chlorination and by-product formation. Since the amination by a tertiary amine is a type of Hofmann reaction, the presence of the chlorine in the 5 position of the ring adds steric hindrance and thus enhances the regiospecificity of the formation of by-products.     

The Standard Enthalpies of Formation of Crystalline Diethylenetriamino-N,N,N′,N″,N″-pentaacetic Acid and Its Dissociation Products

The heat effects of solution of diethylenetriamino-N,N,N′,N″,N″-pentaacetic acid (H₅dtpa) in water and solutions of potassium hydroxide were determined at 298.15 K by direct calorimetry. The standard enthalpies of formation of H₅dtpa and its dissociation products were calculated.     

Quaternary Ammonium Polyelectrolytes. V. Amination Studies of Chloromethylated Polystyrene with N,N-Dimethylalkylamines

The amination reactions of chloromethylated polystyrene with N,N-dimethyldodecylamine, N,N-dimethyltetradecylamine, and N,N-dimethylhexadecylamine were studied. The physical properties, particularly the solubility properties of the resulting polymers, are influenced by the hydrophobic properties of the long alkyl chain on the N⁺ atoms. The main factor that influences the kinetics of the reactions is the polymersolvent interaction parameter.     

Silylation of bicyclic six-membered nitronates. Ring—chain tautomerism of intermediate N,N bis(oxy)iminium cations

Silylation of bicyclic six-membered nitronates was studied as a possible route to conjugated enoximes with a distant carbonyl group. Apart from the target enoximes, this reaction yielded nitro compounds. The ratio of these two types of products and the configurations of their stereogenic centers depend on the nature and configurations of the starting nitronates and the silylation conditions. The results obtained were interpreted in terms of ring—chain tautomerism of intermediate N,N-bis(oxy)iminium cations. Dedicated to Academician O. M. Nefedov on the occasion of his 75th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1983–1992, November, 2006.