New high temperature polymers. VI. Ordered heterocycle copolymers

A new class of linear, thermostable polymers is reported. The compositions are ordered heterocycle copolymers in which two different heterocycles alternate regularly along the polymer chain. Examples of combinations studied are: oxadiazole–benzimidazole, oxadiazole–pyromellitimide, and thiazole–pyromellitimide. The heterocycle copolymers, or alternatively, the corresponding precursor polymers, were prepared by condensing preformed di-or tetrafunctional blocks which contain one type of heterocycle with a second di- or tetrafunctional monomer under such conditions that no rearrangement of bonds occurred. The polymers are characterized in general by neither melting nor decomposing below 500°C. when heated in an inert atmosphere at a rate of about 10°C./min. Some of the copolymers are readily soluble in organic solvents; many, however, are soluble only in solvents such as concentrated sulfuric acid. In the case of the more intractable polymers, soluble precursor polymers can usually be prepared. In such precursor polymers only one of the heterocycles is preformed; the second heterocycle is formed by post-treatment after the polymer has been fabricated into an end product. All of the polymers yielded self-supporting films, some having very high strength; films of several of the polymers were hot-drawable. Drawn film of an ordered oxadiazoleimide copolymer was shown to be well oriented and moderately crystalline.     

Study on the Reaction of Benzimidazolium Salt with Amine Compounds

The addition-hydrolysis reaction of benzimidazolium salt with some mono- and bifunctional amine nucleophiles is reported,and a novel method of biomimetic synthesis for formamides and heterocycle compounds is provided.     

Heterocyclic photorearrangements. Photochemical behaviour of some 3,5-disubstituted 1,2,4-oxadiazoles in methanol at 254 nm

Photochemical behaviour of some 3,5-disubstituted 1,2,4-oxadiazoles in methanol at 254 nm has been investigated. Ring photoisomerization to the 1,3,4-oxadiazole heterocycle or formation of open chain compounds involving the nucleophilic solvent was shown to depend on the nature and the position of the substituent. Photoinduced ring closure into the benzimidazole system, involving a 3-N-phenylamino side chain sequence and a photolytic intermediate of the oxadiazole heterocycle, is also reported.     

2-Methylisoxazolin-5-ones III. Curboxylic. Acids and their Derivatives

Carbethoxy-substituted 12-methylisoxazolin-5-ones and several functional derivatives have been prepared. Spectral properties of the corresponding carboxylic acids are discussed. These acids ant stronger when the carboxy group is in position 3 than when in position 4 of the heterocycle.     

Intermolecular interactions and structural dichotomy in 1,3,2,4-benzodithiadiazine crystals

The intermolecular interactions and structural dichotomy in 1,3,2,4-benzodithiadiazine crystals (1) (the heterocycle is planar for one derivative, but bent for another) were studied in terms of topological analysis of electron density (ED) using QTAIM theory and crystal packing modeling in an OPiX approximation. The intermolecular interactions in crystals 1 can be detected and quantified by means of the critical points (CPs) of ED with (3, ?1). The total value of ED at all CPs of a molecule can be correlated with the torsion angle that defines the bending of its heterocycle; the larger the total ED at intermolecular CPs, the smaller the bending of the heterocycle. Thus, under the conditions of weak intermolecular interactions in crystal, molecules 1 preserve the bent conformations typical of the gas phase; strong intermolecular interactions lead to planar conformations.     

Regioselectivity of Nucleophilic Attack on the Reactions of 1,2,4-Triazine 4-Oxides with Certain C-Nucleophiles

The addition of CH-active compounds to 6-aryl-1,2,4-triazine 4-oxide is reversible and occurs under conditions of kinetic control at position 5 of the heterocycle to form cyclic C(5)-^H adducts. Under conditions of thermodynamic control the nucleophilic attack is directed to position 3 of the heterocycle and is accompanied by its opening to form the more stable open chain addition products. Attack of ethylmagnesium bromide is directed exclusively to the 5 position of the 6-aryl-1,2,4-triazine 4-oxides as a result of the irreversibility of the given reaction.     

Synthesis of 2-methoxy-6-oxo-1, 4, 2-diazaphosphorinane-2-oxide, A New Potential Antitumor Phosphorus Heterocycle Compound

The discoveries that the bisdioxopiperazines ICal- 154', ICal-- 159(razoxane)' and MST16(sobuzoxan)' are inhibitors of mammalian DNA topoisomerase II'-', have led to arenewed interest in these compounds as antitumor agents'. Among the drugs, MST-16(sobuzoxan) was approved in Japan (in 1994) as a potent antit'Umor agent for treatmentof adult T-cell leukemia and malignant lymphoma'. However, the bisdioxopiperazinesexhibited extremely small water-solubility, which reduced its absorption in…     

Preparation, structure, and amphoteric redox properties of p-phenylenediamine-type dyes fused with a chalcogenadiazole unit.

4,7-Bis(dialkylamino)benzo[c][1,2,5]chalcogenadiazoles are a novel class of organic dyes that undergo reversible two-stage one-electron oxidation as well as one-electron reduction. They exhibit absorption maxima in the long-wavelength region, which are assigned as intramolecular charge transfer bands from the phenylenediamine moiety to the electron-accepting heterocycle. Their redox properties as well as molecular and crystal structures are affected by the alkyl substituents on the amino nitrogen and/or by the chalcogen atom (O, S, Se) in the heterocycle.     

4,4,5,5-Tetra(3,5-dibromophenyl)-2,2-diphenyl-1,3-dioxa-2-silole and related compounds as precursors to flame retardant oligomers

Certain strained five-membered heterocycles undergo thermally-induced, carbon-carbon bond homolysis to generate diradicals capable of initiating vinyl polymerization. These compounds usually contain two oxygen atoms and a larger heteroatom (silicon, phosphorus, sulfur) in addition to carbon. If the heterocycle is suitably substituted with halogen (particularly bromine) containing moities it may function as a vehicle to permit incorporation of flame-retarding units into a polymer or oligomer. When an appropriate heterocycle is used as an initiator for radical polymerization each polymer chain formed contains at least one flame-retarding unit. One such heterocycle is 4,4,5,5-tetra(3,5-dibromophenyl)-2,2-diphenyl-1,3-dioxa-2-silole. In instances in which the heterocycle also acts as a monomer, i.e., it is reactive toward chain-propagating radicals, additional flame-retarding activity may be incorporated into the polymer.     

Chemical modification in mass spectrometry. 1.: The double bond location of long-chain fatty acids: The mass spectra of 2-alkenyl substituted heterocycles

A novel approach to double bond location in long-chain olefinic acids has been elaborated by means of “remote functional group modification”. This method consists in converting the carboxylic acid into corresponding 2-alkenyl substituted heterocycle followed by measuring its 70 eV electron-impact mass spectrum. The inherited tendency of random migration of the double bond along the aliphatic chain under electron impact is strongly suppressed by incorporating the terminal carboxyl group into a heterocycle. The derivatives thus prepared show more informative spectra which clearly indicate the site of unsaturation of the parent acids. Submilligram scale derivatization of the olefinic acids, as exemplified by the model compound oleic acid, and a comparison of the spectra of the resulting heterocycles (3—10) as well as benzoxazole derivatives (3a—3d) of selected carboxylic acids is described in the present paper.     

Synthesis of new fundamental heterocycles. Part VII. Synthesis of 2-azaxanthene

2-Azaxanthone ( 5 ) has been conveniently prepared by condensation of the morpholine enamine of 1-benzyl-4-piperidone witli salicylaldehyde followed by chromium trioxide oxidation and subsequent aromatization. Lithium aluminum hydride reduction of 5 afforded the new fundamental heterocycle 2-azaxanlhene.     

Toward new camptothecins. Part 5: On the synthesis of precursors for the crucial Friedländer reaction

The synthesis of potential precursors of ketones, which could be used to obtain camptothecin analogs, is described. Noteworthy is the difference of reactivity between indolizinone and pyrrolidinoquinazolinone heterocycle.     

Rearrangements of N-heteroaromatic-2-vinyl-aziridines. Synthesis of isothiazolo-, pyrido- and thieno-azepines

N-heteroaromatic-2-vinyl-aziridines have been synthesized and thermally isomerized to the corresponding isothiazolo-, pyrido- and thienoazepine derivatives. The ease of rearrangement is strongly dependent on the nature (π-deficient or -rich) of the aromatic heterocycle.     

Studies on Quinones. Part. 33.1 Synthetic Approach to Podands Containing Quinone Fragments

The preparation and oxidative demethylation attempts of podands 3--5, and 9 containing the 2,5-dimethoxyphenyl substituent are described. The reaction of alizarine 13 with chloroethanol afforded compounds 14 and 15. The pathway formation of heterocycle 15 from 14 is proposed. The synthesis of podand 16 containing the cytotoxic 1-hydroxy-9,10-anthraquinone fragment as the terminal groups is reported.     

Phosphorus-containing Derivatives of Indole and Pyrrole. (Review)

Data on the synthesis and chemical properties of the phosphorus-containing derivatives of indoles and pyrroles, published in 1976-1998, are reviewed. The introduction of substituents containing tri- and tetracoordinated phosphorus atom into the heterocycle and the side chain is discussed. Information on the biological activity is presented.     

用碲Ylide合成杂环取代环丙烷衍生物

本文报道了由碲盐和杂环取代查尔酮反应合成杂环取代环丙烷衍生物的简便方法。     

Novel tricyclic diamines 3. Synthesis of 1,4-diazaadamantane

Synthesis of the previously unreported 1,4-diazaadamantane is described. The overall strategy involves complete saturation of a flat, aromatic heterocycle, appropriate functionalization and intramolecular double alkylation. The alkylation takes place via an iminophosphorane under anhydrous conditions, which produced superior results vs. alkylation of the corresponding primary amine.     

A new heterocyclic system: Imidazo[2,1-d][1,5]benzothiazepine. Its synthesis from 4-amino-2,3-dihydro-1,5-benzothiazepine

The synthesis of 4-amino-2,3-dihydro-1,5-benzothiazepine and its transformation to the new heterocycle Imidazo[2,1-d][1,5]benzothiazepine is described.     

Substituted 2-methyl- and 2-methyleneindolines. 3. Nitroamino-5,6-disubstituted 2-methyl- and 2-methyleneindolines

A method is developed for the synthesis of 5,6-disubstituted nitroamino- and nitromethylamino-2-methyl- and-2-methyleneindolines. These are starting compounds for the synthesis of 2-methyleneindolines condensed with some heterocycle.See [1] for Communication 2.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1495–1499, November, 1990.     

Studies on a General Method for the Demethylation of Quaternized Nitrogen Heterocycles

Probably the best general method so far developed for the dealkylation of quaternized nitrogen heterocycles is the reaction of the iodide salts in an aprotic solvent in the presence of triphenylphosphine.^1,2 It has since been established³ that the iodide counterion is the active dealkylating agent, with the triphenylphosphine acting as a “methyl sponge”, preventing the reverse reaction from occurring. It follows, therefore, that any heterocycle (1) ought to be able to fulfil the same role as the triphenylphosphine with respect to the dealkylation of the quaternary salt of a less nucleophilic heterocycle (2). Since the reactivity to methylation of a large number of heterocycles with a reactivity range of ca 10⁶ is known⁴, the choice of a convenient heterocycle (1) to go with any heterocycle (2) is, in principle, a wide one.