Heterocycles

Distribution by Scientific Domains
Distribution within Chemistry

Kinds of Heterocycles

  • aromatic heterocycle
  • fused heterocycle
  • new heterocycle
  • nitrogen heterocycle


  • Selected Abstracts


    ChemInform Abstract: Microwave Mediated Reduction of Heterocycle and Fluorine Containing Nitroaromatics with Mo(CO)6 and DBU.

    CHEMINFORM, Issue 11 2009
    John Spencer
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


    Recyclization of 5-Ethoxycarbonylpyrimidines Occurring with Substitution of a Carbon Atom in the Heterocycle by an Exocyclic Carbon Atom.

    CHEMINFORM, Issue 34 2004
    G. G. Danagulyan
    Abstract For Abstract see ChemInform Abstract in Full Text. [source]


    Novel Chemistry of ,-Tosyloxy Ketones: Applications to the Solution- and Solid-Phase Synthesis of Privileged Heterocycle and Enediyne Libraries.

    CHEMINFORM, Issue 39 2002
    K. C. Nicolaou
    Abstract For Abstract see ChemInform Abstract in Full Text. [source]


    ChemInform Abstract: Synthesis and X-Ray Characterization of a New Polycondensed Heterocycle (II) Obtained by a Novel Mn(III)-Mediated Cascade Reaction of 2-Cyanophenyl Isothiocyanate.

    CHEMINFORM, Issue 50 2001
    Gianluca Calestani
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


    ChemInform Abstract: 3,9-Dihydro-2H-[1,2,4]-oxadiazolo[3,2-b]quinazolin-2-ones: First Synthesis of the Parent Heterocycle, 7- and 9-Substituted Derivatives.

    CHEMINFORM, Issue 13 2001
    Patrice P. Renaut
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


    Reactions of Pendant Boryl Groups in Cp,Metal Complexes: Heterocyclic Ring Annelation in a CpIr System

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2008
    Christoph Herrmann
    Abstract Treatment of (cod)IrCl dimer with Li(allyl)cyclopentadienide gave (C5H4,CH2,CH=CH2)Ir(cod) (11). At 100 C, 11 isomerizes cleanly into its ring-conjugated (trans -CH3,CH=CH,C5H4)Ir(cod) isomer (13). Subsequent addition of HB(C6F5)2 results in the formation of a product (16) that contains an annelated five-membered borata heterocycle at the Cp ring. This is probably formed by means of a reaction sequence involving regioselective hydroboration, followed by an electrophilic substitution reaction at the Cp ring by the strongly Lewis acidic ,B(C6F5)2 group, in which the iridium metal base acts as the proton abstractor. Products 13 and 16 were characterized by X-ray diffraction. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]


    Selenium Heterocycles: Reactions of SeX4 (X = Cl, Br) with the Enamine Form of ,-Diketiminato Ligands

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2008
    Audra F. Gushwa
    Abstract Treatment of SeX4 (X = Cl, Br) with either MesnacnacLi(nacnac = [{N(Ar)C(Me)}2CH],, Ar = Mes = C6H2Me3 -2,4,6) or DmpnacnacLi (Ar = Dmp = C6H3Me2 -2,6) affords four new SeII six-membered heterocycles, [MesnacnacHCl2SeCl] (2), [MesnacnacH2Se]+Br, (3), [DmpnacnacH2Cl3Se]+Cl, (4), and [MesnacnacH2(O)Br2Se] (5). All have been characterized in the solid state by X-ray crystallography. Each of the four complexes is proposed to have formed from the initial reaction of SeX4 with the C,C double bond that results from the enamine form of the ligand, giving rise to an Se,C single bond. Subsequent nucleophilic attack by either the more distant nitrogen atom or the remaining C,C double bond of the enamine form results in the Se heterocycle. In complexes 2, 4, and 5 varying degrees of halogenation of the newly formed heterocycles was observed.( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]


    Synthesis of 3-(Tosylalkyl)indazoles and their Desulfonylation Reactions , A New Entry to 3-Substituted Indazoles by an Unprecedented Friedel,Crafts Process

    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 19 2009
    Silvia Campetella
    Abstract Reaction of indazoles with aldehydes in the presence of p -toluenesulfinic acid affords the corresponding sulfonyl indazoles in satisfactory yields. The reported Friedel,Crafts process is rather unusual on indazoles because of the reduced electronic density of the heterocycle. The obtained sulfonyl indazoles can be desulfonylated under reductive conditions, finally leading to 3-alkylated indazoles.( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]


    Indole in DNA: Comparison of a Nucleosidic with a Non-Nucleosidic DNA Base Substitution

    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 3 2009
    Janez Barbaric
    Abstract The synthetic incorporation of indole as an artificial DNA base into oligonucleotides by two different structural approaches is described. For both types of modification, the indole moiety is attached through the C-3 position to the oligonucleotides. As a mimic of natural nucleosides, the indole nucleoside of ,-2,-deoxyribofuranoside (In) was synthesized. The corresponding In-modified duplexes were compared with duplexes that contained the indole group connected through (S)-3-amino-1,2-propanediol as an acyclic linker between the phosphodiester bridges of the oligonucleotides. This linker was tethered to the C-3 position of the indole heterocycle either directly (In,) or by a carbamate function (In,). The melting temperatures of the corresponding indole-modified DNA duplexes were measured and compared. Interestingly, not only the In, and In, modifications but also the natural-like In base surrogate destabilize the DNA duplex strongly. This result supports our approach to apply the acyclic glycol linker to incorporate aromatic molecules as artificial DNA base substitutions. The major advantage of acyclic glycol linkers [such as the applied (S)-3-amino-1,2-propanediol] is that the corresponding modifications are synthetically more easily and readily accessible, as it avoids the preparation of the nucleosidic bond and the separation and purification of the ,- and ,-anomers. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]


    Microwave-Assisted Paal,Knorr Reaction , Three-Step Regiocontrolled Synthesis of Polysubstituted Furans, Pyrroles and Thiophenes

    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 24 2005
    Giacomo Minetto
    Abstract An efficient and highly versatile synthesis of furans, pyrroles and thiophenes is described. Starting from commercially available or easily prepared ,-keto esters, functional homologation provides differently substituted 1,4-diketones that can be transformed, through a microwave-assisted Paal,Knorr condensation, into the corresponding methoxycarbonyl heterocycles. The methoxycarbonyl moiety can be directly transformed into an NH2 group by hydrolysis to carboxylic acid and Curtius rearrangement or into an amide by reaction with a primary amine in the presence of Me3Al. The method is compatible with the presence of a CbzNH group so that the final heterocycle can be inserted into a peptide sequence as a turn inducer. By using this procedure, a collection of more than 60 different tetrasubstitued pyrroles or trisubstituted thiophenes has been prepared. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]


    Structural Studies on Hydrogen-Bonding Receptors for Barbiturate Guests That Use Metal Ions as Allosteric Inhibitors

    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 1 2004
    Mohammad H. Al-Sayah
    Abstract Receptor 1 was designed to bind barbiturate substrates through a six-point hydrogen-bonding motif only in the absence of metal allosteric cofactors. It was predicted that the binding of metal ions by bipyridine ligands in 1 would result in a geometric change in the receptor to inhibit substrate recognition. However, receptor 1 showed minimal affinity for the barbiturate guests even in the absence of the metal. Binding studies on model compounds 2, 3, 5, and 6 revealed that the inactivity of 1 is due to an intramolecular hydrogen bond between the N,H donor groups and the nitrogen atoms on the first heterocycle of the bipyridine ligands. This intramolecular hydrogen-bonding was eliminated by altering the position of the tether between the bipyridine ligands and the active site to produce receptor 7. Consequently, the high affinity exhibited by 7 for the barbiturate substrate (Ka = 2.80.7 103M,1 in 9:1 CD2Cl2/CD3CN) was significantly reduced by the addition of ZnII ions as a negative allosteric co-factor. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]


    Synthesis and Properties of Oligodeoxynucleotide Analogs with Bis(methylene) Sulfone Bridges

    HELVETICA CHIMICA ACTA, Issue 9 2003
    Bernd Eschgfller
    A convergent, solution-phase synthesis was developed for the bis(methylene) sulfone-bridged oligodeoxynucleotide analogs (SNA) 5,-d(HOCH2 -Tso2Tso2Tso2Cso2Tso2Tso2Tso2T-CH2SO)-3, (35b) and 5,-d(HOCH2 -Tso2Tso2Tso2Tso2Tso2Tso2Tso2T-CH2SO)-3, (34c) (SO2 corresponds to CH2SO2CH2 instead of OP(O)(O,)(O). In these, the phosphodiester linkages are replaced by non-ionic bis(methylene) sulfone linkers. The general strategy involved convergent coupling of 3,,5,-bishomo- , - D -deoxyribonucleotide analogs functionalized at the 6,-end (CH2C(5,)) as bromides or mesylates and at the CH2C(3,) position as thiols, with the resulting thioether being oxidized to the corresponding sulfone. A single charge was introduced at the terminal CH2C(3,) position of the octamers to increase their solubility in water. During the synthesis, it became apparent that the key intermediates generated secondary structures through either folding or aggregation in a variety of solvents. This generated unusual reactivity and was unique for very similar structures. For example, although the dimeric thiol d(BzOCH2 -Tso2C-CH2SH) (14b) was a well-behaved synthetic intermediate, the tetrameric thiol d(TrOCH2 -Tso2Tso2Tso2toC-CH2SH) derived from the corresponding thioacetate was rapidly converted to a disulfide by very small amounts of oxidant (28,29, Scheme,6), while the analogous tetrameric thiol d(BzOCH2 -Tso2TsTso2T-CH2SH) (26), differing only by a single heterocycle, was oxidized much more slowly (Bz=PhCO, Tr=Ph3C, to=2-MeC6H4CO (at N4 of dc)). The sequence-dependent reactivity, well known in many classes of natural products (including polypeptides), is not prominent in natural oligonucleotides. These results are discussed in light of the proposal that the repeating negative charge in nucleic acids is key to their ability to serve as genetic molecules, in particular, their capability to support Darwinian evolution. The ability of 5,-d(HOCH2 -Tso2Tso2Tso2Cso2Tso2Tso2Tso2T-CH2SO)-3, (35b) to bind as a third strand to duplex DNA was also examined. No triple-helix-forming propensity was detected in this molecule. [source]


    An efficient synthesis and crystal structure of novel 1-oxo-2-propyl-4-(substituted)phenylimino-1,2,3,4,5,6,7,8-octahydro[1,4,3]thiazaphosphorino[4,3- a][1,3,2]benzodiazaphosphorine 3-oxides,

    HETEROATOM CHEMISTRY, Issue 7 2002
    Junmin Huang
    A series of 1-oxo-2-propyl-4-(substituted)phenylimino-1,2,3,4,5,6,7,8-octahydro-[1,4,3]thiazaphosphorino[4,3-a][1,3,2]benzodiazaphosphorine 3-oxides (5a,g) has been synthesized in excellent yields via the reaction of 1-(2-bromoethyl)-2,3-dihydro-3-propyl-1,3,2-benzodiazaphosphorin-4(1H)-one 2-oxide with (substituted) phenyl isothiocyanates, which contain the proximate imino and phosphoryl groups in the fused heterocycle. The structures of all of the new compounds were confirmed by spectroscopic methods and microanalyses. The results from X-ray crystallography analysis of 5a showed that the proximate imino and phosphoryl groups are not coplanar due to their being jointly located in the fused heterocycle, thus having ring tension, and this then destroys the conjugation between the CN and the PO moieties. As a result, the length of the PC bond, measured as 1.8285(18) , is just the same as that of a PC bond not involved in conjugation (1.80,1.85 ). Also, the C(1), C(2), S(1), C(3), P(1), and N(2) atoms of the [1,4,3]thiazaphosphorino moiety exist preferably in the boat conformation. The coplanar C(1), N(2), C(3), and S(1) atoms, within an average deviation of 0.0564 , form the ground floor of the boat conformation, whereas, the P(1) and C(2) atoms are on the same side of the coplanar structure with the distance of 0.7729 and 0.7621 , respectively. On the other hand, around the CN double bond, the P(1)C(3) bond and the N(1)C(11) bond are in a trans relationship because of the repulsive action of the n-propyl group in the 2-position of the title compound. 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:599,610, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10041 [source]


    Substituted 1,3,2,4-benzodithiadiazines: Novel derivatives, by-products, and intermediates,

    HETEROATOM CHEMISTRY, Issue 7 2001
    Alexander Yu.
    The synthesis of the title compounds 1 by 1:1 condensation of ArNSNSiMe3 2 with SCl2 followed by intramolecular ortho-cyclization of each [ArNSNSCl] intermediate is complicated by further reaction of 1 with SCl2 to give Herz salts 3. With the 2:SCl2 ratio of 2:1, the formation of by-products 3 is reduced and novel compounds 1 are accessible. With ortho-I containing starting material 2j, the parent compound 1s is obtained as the result of an unexpected I, not H, substitution. The rate of the 1 + SCl2 reaction depends upon a substituent's position, and the minor 8-R isomers 1l,p (R = Br, I) are isolated for the first time from mixtures with the major 6-R isomers due to reduced reactivity toward SCl2. The synthesized compounds 1,3 are characterized by multinuclear (including nitrogen) NMR and X-ray crystallography. According to the X-ray diffraction data, 1j (6-Br) and 1k (7-Br) derivatives are planar, whereas 1i (5-Br) and 1l (8-Br) are bent along the S1N4 line by ,5 and ,4, respectively, and the 1r (7-OCH3) derivative is planar in contrast to the known 5-OCH3 isomer, which possesses a significantly folded heterocycle. The distortion of the planar geometry of some compounds 1 is interpreted in terms of a pseudo-Jahn-Teller effect as the result of ,-highest occupied molecular orbital (HOMO) ,*-(LUMO) lowest unoccupied molecular orbital + 1 mixing in a planar conformation. The 2p compound is the first structurally defined Ar,N = S = N,SiMe3 azathiene. The compound Ar,N = S = N,S,NH-Ar 6 modeling the aforementioned intermediate has been isolated and structurally characterized. We describe the attempts to synthesize compounds 1 from 2-aminobenzenethiols and (SN)4 and from salts 3 and Me3SiN3, and we discuss the reaction pathways. 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:563,576, 2001 [source]


    A practical and stereoselective synthesis of (+/,)- trans -4-benzyloctahydropyrrolo[3,4- b][1,4]oxazine

    JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 5 2010
    Daniel P. Walker
    trans -Octahydropyrrolo[3,4- b][1,4]oxazine is an important heterocycle within the pharmaceutical industry for the preparation of biologically active analogs, including the phase III drug, finafloxacin. A practical synthesis of the title compound (2) is described in eight steps and ca. 10% overall yield. The key synthetic step is the formation of the pyrrolo[3,4- b][1,4]oxazine core 20via a one pot double N -alkylation of the corresponding bis-tosylate 18 with 4-nitrobenzenesulfonamide. Subsequent removal of the nosyl group occurred under mild conditions. J. Heterocyclic Chem., (2010). [source]


    1,3-Dipolar cycloaddition reaction of 4,5-dihydro-1H -imidazole 3-oxides with alkynes

    JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 2 2006
    Sergey A. Popov
    4,5-Dihydro-1H -imidazole 3-oxides bearing different substituents at positions 1 and 2 of the heterocycle were shown to react with a wide range of acceptor-substituted alkynes forming corrsponding cycloadducts - derivatives of 1,2,3,7a-tetrahydroimidazo[1,2- b]isoxazole. High regioselectivity of this process stipulated by conjugation of the nitrogen atom with the nitrone group was revealed. [source]


    Synthesis, characterization, and structural investigations of 1-amino-3-substituted-1,2,3-triazolium salts, and a new route to 1-substituted-1,2,3-triazoles

    JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 1 2005
    Greg Kaplan
    Quarternary salts based upon 3-alkyl substituted 1-amino-1,2,3-triazolium cations (alkyl = methyl, ethyl, nypropyl, 2-propenyl, and n -butyl) have been synthesized and characterized by vibrational spectra, multinuclear NMR, elemental analysis, and DSC studies. Subsequent diazotization of these salts results in the exclusive formation of 1-alkyl-1,2,3-triazoles. Single crystal X-ray studies were carried out for 1-amino-3-methyl-1,2,3-triazolium iodide, 1-amino-3-ethyl-1,2,3-triazolium bromide, 1-amino-3- n -propyl-1,2,3-triazolium bromide, and 1-amino-3- n -butyl-1,2,3-triazolium bromide as well as the starting heterocycle, 1-amino-1,2,3-triazole, and all of the structures are discussed. [source]


    Preparation and structure elucidation of 1,6,9,13-tetraoxadispiro(4.2.4.2)tetradecane

    JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 5 2000
    Bruce Gaede
    The tricyclic title compound, a symmetrical dispiro oxygen heterocycle, was isolated as a byproduct in the hydrogenation of furfuryl alcohol in the presence of hydrochloric acid. NMR studies and single crystal X-ray analysis have established the relative stereochemistry of the two ketal carbons. Formation of the observed trans stereoisomer under equilibrating conditions is attributed to the anomeric effect. [source]


    Proton and metal-ion activation of C,H exchange in five-membered azoles

    JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 4 2002
    Erwin Buncel
    Abstract Factors influencing C,H isotopic exchange rates in five-membered azoles, that is imidazoles and thiazoles, under catalysis by H+ and Mn+, especially transition metals, Pt(II) and Co(III) are discussed. Hydrogen ion catalysis through N(3) protonation of azoles 1,3 is generally the most efficient, with rate enhancements in the range 102,109 over the neutral process being attained. Metal-ion coordination also results in effective catalysis, though less so than catalysis by protons. Catalysis of C,H exchange by Mn+ can be studied through addition of the metal salts to a buffered solution of the heterocycle in which labile complexes exist, or on synthesized complexes such as 4,13 which are substitution-inert thus precluding complications from unknown dissociation equilibria. A delicate balance of factors influence the ease of C,H exchange, including: (1) the magnitude of the fractional charge located at N(3) of the heterocycle through Mn+,N(3) , bond polarization; (2) metal-to-ligand , back-bonding; (3) the electronic structure of the metal ions. These considerations have obvious consequences for deuterium- and tritium-labelling of a number of biomolecules, e.g. proteins, enzymes, nucleic acids, some vitamins, as well as drugs which incorporate five-membered azoles in their structures. Copyright 2002 John Wiley & Sons, Ltd. [source]


    Substituent effect on local aromaticity in mono and di-substituted heterocyclic analogs of naphthalene

    JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 5 2010
    Afshan Mohajeri
    Abstract A quantitative study on local aromaticity has been performed on a series of mono- and di-substituted biheterocycles (quinoline, isoquinoline, quinoxaline, quinazoline). Three electronically based indices (PDI, ATI, and FLU) have been employed to investigate the substituent effect on the , -electron delocalization in both heterocycle and benzenoid rings. Three typical substituents (Cl, OCH3, and CN) with different inductive and resonance power have been selected. Generally, substituent causes a reduction in aromaticity irrespective of whether it is electron attracting or electron donating. It is shown that the maximum aromaticity exhibits a similar trend of Cl,>,CN,>,OCH3 for all the studied rings. Moreover, it is found that the substituent situation with respect to the heteroatom has a significant influence on the aromaticity. It results from our study that in di-substituted derivatives, irrespective of whether the two substituents form a meta or para isomer, they preferably choose the position which leads to the maximum aromaticity character. Copyright 2009 John Wiley & Sons, Ltd. [source]


    Redox reactions of copper(II) upon electrospray ionization in the presence of acridine ligands with an amide side chain

    JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 3 2009
    Aura Tintaru
    Abstract The complexation of copper(II) to acridine derivatives has been studied by means of electrospray ionization (ESI) mass spectrometry. Under soft conditions of ionization, the ESI mass spectra of methanolic solutions of copper(II) chloride and the acridine ligands show abundant signals of the mononuclear complexes formed from the metal and ligand. Depending on the position of the N -benzoylamino substituent in the acridinic heterocycle, however, the copper atom involved in the complexation process adopts different oxidation states in the resulting cations. Hence, the metal is reduced to copper(I) in the monocationic complex with the compound substituted in position 2, whereas it keeps its divalent state in the monocation formed with the compound substituted in position 4. As a consequence, the regioisomers lead to monocations with different masses in the ESI spectra. In order to understand this unusual behavior of two isomeric compounds, additional experiments have been performed with quinoline as a model. Copyright 2008 John Wiley & Sons, Ltd. [source]


    Quinoxaline 1,4-dioxides: Hypoxia-selective therapeutic agents

    MOLECULAR CARCINOGENESIS, Issue 4 2002
    Mona Diab-Assef
    Abstract A problem that confronts clinicians in the treatment of cancer is the resistance of hypoxic tumors to chemotherapy and radiation therapy. Thus, the development of new drugs that are toxic to hypoxic cells found in solid tumors is an important objective for effective anticancer chemotherapy. We recently showed that the heterocyclic aromatic N-oxides, quinoxaline 1,4-dioxides (QdNOs), are cytotoxic to tumor cells cultured under hypoxia. In this study, we evaluated the hypoxia-selective toxicity of four diversely substituted QdNOs and determined their effect on the expression of hypoxia inducible factor (HIF) 1, in the human colon cancer cell line T-84. The various QdNOs were found to possess a 50- to 100-fold greater cytotoxicity to T-84 cells cultured under hypoxia compared with oxia. Interestingly, the hypoxia cytotoxicity ratio (HCR), the ratio of equitoxic concentrations of the drug under aerobic/anoxic conditions, was highly structure related and depended on the nature of the substituents on the QdNO heterocycle. The most cytotoxic 2-benzoyl-3-phenyl-6,7-dichloro derivative of QdNO (DCQ) was potent at a dose of 1 ,M with an HCR of 100 and significantly reduced the levels of HIF-1, transcript and protein. The 2-benzoyl-3-phenyl derivative (BPQ) had a hypoxia potency of 20 ,M and an HCR of 40. By contrast, the 2-aceto-3-methyl and the 2,3-tetramethylene (TMQ) derivatives of QdNO were much less cytotoxic under hypoxia (HCRs of 8.5 and 6.5, respectively) and reduced the expression of HIF-1, mRNA to a much lesser extent. Because the nonchlorinated analogue BPQ did not demonstrate behavior similar to that of DCQ, we hypothesize that the C-6, C-7-chlorine of DCQ might play a significant role in the selective hypoxic cytotoxicity of the drug. 2002 Wiley-Liss, Inc. [source]


    Structural and Preliminary Explosive Property Characterizations of New 3,4,5-Triamino-1,2,4-triazolium (Guanazinium) Salts

    PROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 5 2008
    Chaza Darwich
    Abstract Two new highly stable energetic salts were synthesized in reasonable yield by using the high nitrogen-content heterocycle 3,4,5-triamino-1,2,4-triazole and resulting in its picrate and azotetrazolate salts. 3,4,5-Triamino-1,2,4-triazolium picrate (1) and bis(3,4,5-triamino-1,2,4-triazolium) 5,5,-azotetrazolate (2) were characterized analytically and spectroscopically. X-ray diffraction studies revealed that protonation takes place on the nitrogen N1 (crystallographically labelled as N2). The sensitivity of the compounds to shock and friction was also determined by standard BAM tests revealing a low sensitivity for both. B3LYP/6,31G(d,,p) density functional (DFT) calculations were carried out to determine the enthalpy of combustion (,cH(1)=,3737.8,kJ mol,1, ,cH(2)=,4577.8,kJ mol,1) and the standard enthalpy of formation (,fH(1)=,498.3,kJ mol,1, (,fH(2)=+524.2,kJ mol,1). The detonation pressures (P(1)=189108,Pa, P(2)=199108,Pa) and detonation velocities (D(1)=7015,m s,1, D(2)=7683,m s,1) were calculated using the program EXPLO5. [source]


    Properties of Some Alkyl Substituted Phthalocyanines and Related Macrocycles

    THE CHEMICAL RECORD, Issue 4 2002
    Michael J. Cook
    Abstract This report provides an account of research undertaken at the University of East Anglia, United Kingdom, into phthalocyanine derivatives substituted at six or more of the nonperipheral sites by alkyl groups. When first prepared they were only the second series of substituted phthalocyanines known to exhibit columnar liquid crystal behaviour. The compounds also form structured films by the spin-coating technique, a formulation with potential for FET devices. The zinc metallated derivatives are photosensitisers of singlet oxygen and show good potential for applications in photodynamic therapy. A mixed cyclotetramerisation of a 3,6-dialkylphthalonitrile with a second aromatic dinitrile forms so-called 3,:,1 phthalocyanines in which three of the benzenoid rings are substituted with two alkyl groups and the fourth is substituted differently. Appropriate substituents provide amphiphilic compounds that form well-ordered films by the Langmuir-Blodgett method and self-assembly techniques. Characterisation of the films using a variety of methods is discussed and applications described. Examples of 3,:,1 phthalocyanine-like macrocycles in which one of the benzenoid rings is replaced by a heterocycle extend the range of properties exhibited. These include broadband absorption in the near infrared and, in particular cases, edge-to-face dimerisation through coordination of a pyridine nitrogen to a zinc centre in a second macrocycle. The potential for using suitably functionalised 3,:,1 phthalocyanines as building blocks for more complex structures such as liquid crystalline main-chain polymeric phthalocyanines and phthalocyanino-dehydroannulenes is described. 2002 The Japan Chemical Journal Forum and Wiley Periodicals, Inc., Chem Rec 2: 225,236, 2002: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.10028 [source]


    A third polymorph of 4-(2,6-difluorophenyl)-1,2,3,5-dithiadiazolyl

    ACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2010
    Elisabeth M. Fatila
    The crystal structure of a third polymorphic form of the known 4-(2,6-difluorophenyl)-1,2,3,5-dithiadiazolyl radical, C7H3F2N2S2, is reported. This new polymorph represents a unique crystal-packing motif never before observed for 1,2,3,5-dithiadiazolyl (DTDA) radicals. In the two known polymorphic forms of the title compound, all of the molecules form cis -cofacial dimers, such that two molecules are ,-stacked with like atoms one on top of the other, a common arrangement for DTDA species. By contrast, the third polymorph, reported herein, contains two crystallographically unique molecules organized such that only 50% are dimerized, while the other 50% remain monomeric radicals. The dimerized molecules are arranged in the trans -antarafacial mode. This less common dimer motif for DTDA species is characterized by ,,, interactions between the S atoms [S...S = 3.208,(1), at 110,K], such that the two molecules of the dimer are related by a centre of inversion. The most remarkable aspect of this third polymorph is that the DTDA dimers are co-packed with monomers. The monomeric radicals are arranged in one-dimensional chains directed by close lateral intermolecular contacts between the two S atoms of one DTDA heterocycle and an N atom of a neighbouring coplanar DTDA heterocycle [S...N = 2.857,(2) and 3.147,(2), at 110,K]. [source]


    (,5 -Cyclopentadienyl)[(1,2,3,4,4a,10a-,)-1-methylthianthrene]iron(II) hexafluoridophosphate acetone 0.33-solvate

    ACTA CRYSTALLOGRAPHICA SECTION C, Issue 12 2009
    Arthur D. Hendsbee
    The title complex salt, [Fe(C5H5)(C13H10S2)]PF60.33C3H6O, obtained from an acetone,diethyl ether,dichloromethane mixture at 280,(2),K, has three cationic molecules (A,C), three hexafluoridophosphate counter-anions and one acetone solvent molecule in the asymmetric unit. Two of the three cations contain FeCp (Cp is cyclopentadienyl) inside the fold of the heterocycle. The dihedral angles between the planes of the external (complexed and uncomplexed) benzene rings in the thianthrene molecule are 146.5,(2) for FeCp-out-of-fold molecule A, and 139.0,(3) and 142.5,(2) for the two FeCp-in-fold molecules B and C, respectively. The complexed Cp and benzene rings in each molecule are almost parallel, with a dihedral angle between the planes of 0.2,(5) for molecule A, 2.8,(5) for B, and 2.19,(4) and 6.86,(6) for the disordered Cp ring in C. [source]


    A toyocamycin analogue with the sugar moiety in a syn conformation

    ACTA CRYSTALLOGRAPHICA SECTION C, Issue 9 2009
    Frank Seela
    The title compound [systematic name: 4-amino-5-cyano-1-(,- d -ribofuranosyl)-7H -pyrrolo[2,3- d]pyrimidine hemihydrate], C12H13N5O40.5H2O, is a regioisomer of toyocamycin with the ribofuranosyl residue attached to the pyrimidine moiety of the heterocycle. This analogue exhibits a syn glycosylic bond conformation with a , torsion angle of 57.51,(17). The ribofuranose moiety shows an envelope C2,- endo (2E) sugar conformation (S -type), with P = 161.6,(2) and ,m = 41.3,(1). The conformation at the exocyclic C4,,C5, bond is +sc (gauche, gauche), with a , torsion angle of 54.4,(2). The crystal packing is stabilized by intermolecular O,H...O, N,H...N and O,H...N hydrogen bonds; water molecules, located on crystallographic twofold axes, participate in interactions. An intramolecular O,H...N hydrogen bond stabilizes the syn conformation of the nucleoside. [source]


    N4 -Methyl- N4 -(2-methylphenyl)-1H -pyrazolo[3,4- d]pyrimidine-4,6-diamine,ethanol,hydrazine (1/0.865/0.135): hydrogen-bonded ribbons containing four independent ring types

    ACTA CRYSTALLOGRAPHICA SECTION C, Issue 6 2009
    Jorge Trilleras
    N4 -Methyl- N4 -(2-methylphenyl)-1H -pyrazolo[3,4- d]pyrimidine-4,6-diamine crystallizes from ethanol as a mixed solvate, C13H14N60.865C2H6O0.135N2H4, (I), where the hydrazine has been carried through from the initial preparation. Within the heterocyclic component, the 2-methylphenyl substituent is disordered over two sets of sites. There is an intramolecular C,H...,(arene) hydrogen bond, which may control the molecular conformation of the heterocycle. The heterocyclic molecules are linked by two independent N,H...N hydrogen bonds in a chain containing two types of R22(8) ring. The ethanol component is linked to this chain by a combination of O,H...N and N,H...O hydrogen bonds and the hydrazine component by two N,H...N hydrogen bonds, so generating two R33(9) rings and thus forming a ribbon containing four distinct ring types. [source]


    Nickel and zinc complexes with a monodentate heterocycle and tridentate Schiff base ligands: self-assembly to one- and two-dimensional supramolecular networks via hydrogen bonding

    ACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2009
    Xiao-Hua Chen
    In the complex (morpholine)[2-hydroxy- N,-(5-nitro-2-oxidobenzylidene)benzohydrazidato]nickel(II), [Ni(C14H9N3O5)(C4H9NO)], (I), the NiII center is in a square-planar N2O2 coordination geometry. The complex bis[,-2-hydroxy- N,-(2-oxidobenzylidene)benzohydrazidato]bis[(morpholine)zinc(II)], [Zn2(C14H10N2O3)2(C4H9NO)2], (II), consists of a neutral centrosymmetric dimer with a coplanar Zn2(,2 -O)2 core. The two ZnII centers are bridged by phenolate O atoms. Each ZnII center exhibits a distorted square-pyramidal stereochemistry, in which the four in-plane donors come from the O,N,O,-tridentate 2-hydroxy- N,-(2-oxidobenzylidene)benzohydrazidate(2,) ligand and a symmetry-related phenolate O atom, and the axial position is coordinated to the N atom from the morpholine molecule. There are intramolecular phenol,hydrazide O,H...N hydrogen bonds present in both (I) and (II). In (I), square-planar nickel complexes are linked by intermolecular morpholine,morpholine N,H...O hydrogen bonds, leading to a one-dimensional chain, while in (II) an infinite two-dimensional network is formed via intermolecular hydrogen bonds between the coordinated morpholine NH groups and the uncoordinated phenolate O atoms. [source]


    Hydrogen bonding in 2-(2-oxothiazolidin-3-yl)-4,5-dihydrothiazolium hydrogen sulfate monohydrate

    ACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2008
    Rodrigo S. Corra
    The asymmetric unit of the title compound, C6H9N2OS2+HSO4,H2O, contains a heterocyclic cation, a hydrogen sulfate anion and a water molecule. There are strong hydrogen bonds between the hydrogen sulfate anions and water molecules, forming an infinite chain along the [010] direction, from which the cations are pendent. The steric, electronic and geometric features are compared with those of similar compounds. In this way, structural relationships are stated in terms of the influence of the sulfate group on the protonation of the heterocycle and on the tautomeric equilibrium in the solid state. [source]