Liberato Cardellini

The reaction of 1,1,2,2-ethenetetracarbonitrile (TCNE) with aminopyridines: Salts and charge transfer complex formation☆

Abstract Aminopyridines form molecular complexes in solution with 1,1,2,2-ethenetetracarbonitrile (TCNE). Depending on the donor, the formation of pyridinium salts of the pentacyanopropenide anion may be competitive, or, in some cases, the sole reaction. This behaviour is discussed in terms of the basicity and geometry of aminopyridines. Formation constant and thermodynamic parameters were determined for the most stable complex with 2-dibenzoylaminopyridine-1-oxide.

Molecular associations of 5-membered benzofused heterocyclic donors with organic acceptors

Benzofused heterocycles like 10H-[1]benzo thieno[3,2-b] indole and thieno[3,2-b]benzo[b]thiophene form molecular associations with π* organic acceptors. The weak interactions involved are viewed in terms of UV-Vis and IR techniques. The results, mainly in the case of complexes of 10H-[1]benzo thieno[3,2-b] indole, are in some disagreement with the literature. The structure of the complex 10H-[1]benzo thieno[3,2-b] indole/tetracyanoethylene is also reported. The four condensed rings constitute a conjugate system with significant lengthenings of the aromatic ring bonds and a shortening of those of the five-membered rings. The fragment as a whole is almost planar, and forms a dihedral angle of 39.9(1)° with the planar tetracyanoethylene molecule.

Reactions of N-Nitrosodiphenylamine with Grignard Reagents. A Convenient Synthesis of Diaryl- and Dialkyl Nitroxyls

Abstract N-nitrosodiphenylamine reacts with Grignard reagents forming symmetric dialkyl- or diarylhydroxylamines which are quantitatively converted into the corresponding nitroxyls by lead dioxide oxidation.

FT-IR Study on Triple Complexes Between Vesicles, Polynucleotides and Metal Ions

The FT-IR spectra of complexes between polynucleotides (polyadenilic and polyuridilic monophosphoric acids, calf thymus DNA) with metal cations and phosphatidylcholine are investigated. By changes in the main vibrational modes, the influence of the metal as well as of the vesicle on the spectral features of the complex can be elucidated.

Radical-chain decomposition of cyclohexa-1,4-diene-3-carboxylates and 2,5-dihydrofuran-2-carboxylates

3-Methylcyclohexa-1,4-diene-3-carboxylates and 2-methyl-2,5-dihydrofuran-2-carboxylates decompose to generate free alkyl radicals which have been incorporated into chain reactions producing alkyl bromides, alkene adducts and ring-closure products.

Alkyl radical generation using cyclohexa-1,4-diene-3-carboxylates and 2,5-dihydrofuran-2-carboxylates

3-Methylcyclohexa-1,4-diene-3-carboxylic acid and 2-methyl-2,5-dihydrofuran-2-carboxylic acid were prepared by Birch reduction and alkylation of benzoic and furoic acid respectively and converted to alkyl esters. Cyclohexadienyl and 2,5-dihydrofuranyl radicals were generated by hydrogen abstraction and characterised by EPR spectroscopy. The esters decomposed thermally in the presence of a radical initiator to generate alkyl radicals which could be trapped with moderate efficiency by halogen donors or alkenes. Loss of methyl to afford an alkyl benzoate was an important side reaction at higher temperatures. From the thermal reaction of hex-5-enyl 3-methylcyclohexa-1,4-diene-3-carboxylate the rate constant for hydrogen abstraction from the ester by hexenyl radicals was determined to be 0.82 × 105 dm3 mol-1 s-1 at 140 °C.

N-NITROSODIPHENYLAMINE AS AN ALTERNATIVE NITROSATING AGENT FOR INDOLES

Abstract N-nitrosodiphenylamine reacts in the presence of catalytic amounts of trichloroacetic acid with indoles forming the corresponding nitroso and iso-nitroso derivatives in good yields.

Nitrenium ions. Part 1. Acid-catalysed reactions of 2-methylindole with nitrosobenzenes. Crystal structures of 2-phenylamino-3-phenylimino-3H-indole, 2-(o-tolylamino)-3-(o-tolylimino)-3H-indole, N-phenyl-N-(2-phenylamino-3H-indol-3-ylidene)amine N-oxide and bis(2-methyl-1H-indol-3-yl)methane

2-Methylindole 3b reacts with nitrosobenzenes 1a–c in the presence of monochloroacetic acid affording compounds which are characterized by the formation of carbon–nitrogen bonds and other compounds which clearly could arise from a radical mechanism. The radical component of the reaction is also supported by the EPR spectroscopy as well as the reaction products distribution. Although these reactions cannot be considered of synthetic value for the number of isolated products, they could be regarded as clear examples of the electrophilic character and of the oxidative power of nitrogen in activated nitrosobenzenes. Crystal structures of 2-phenylamino-3-phenylimino-3H-indole 7a, 2-(o-tolylamino)-3-(o-tolylimino)-3H-indole 7b, N-phenyl-N-(2-phenylamino-3N-indol-3-ylidene)amine N-oxide 9a and bis(2-methyl-1H-indol-3-yl)methane 10 are also reported.

Molecular Interactions Between Arylazopyridines and N-Hydroxyindoles

SummaryThe reaction of isomeric arylazopyridines with 1-hydroxy-2-phenylindole leads to molecular associations between the pyridine derivative and the 1-hydroxy-2-phenylindole itself or its dimer. The role of hydrogen bonding in the formation of the complex is also discussed in the light of conductivity measurements.ZusammenfassungDie Reaktion isomerer Arylazopyridine mit 1-Hydroxy-2-phenylindol führt zu molekularen Associaten zwischen den Pyridin-Derivaten und 1-Hydroxy-2-phenylindol oder seinem Dimer. Die Rolle der Hydrogenbindung bei der Bildung der Komplexverbindung wird mittels Leitfähigkeitsmessungen geprüft.

Radical cations. Part 2. Oxidative dimerization of indolizines: a chemical and electrochemical investigation

3-Unsubstituted indolizines undergo oxidative dimerization in the presence of catalytic amounts of FeIII and oxygen. Although much experimental evidence apparently indicates that FeII is reoxidised to FeIII by oxygen, a chain mechanism cannot be envisaged. A chain sequence can be proposed only in the case where a stoicheiometric amount of FeIII is used.