Publications 2006

2006

Microwave assisted synthesis and crystal structures of 2-imidazolines and imidazoles

Antonio de la Hoz, Angel Diaz-Ortiz, Maria Mateo, Monica Moral, Andres Moreno, Jose Elguero, Concepcion Foces-Foces, Matias Rodriguez, Ana Sanchez-Migallon. A series of 2-imidazolines and imidazoles has been synthesized using green synthetic methodologies.  The prepn. of 2-imidazolines was performed by cyclization of nitriles with ethylenediamine.  The use of microwave irradn. in solvent-free conditions enabled 2-imidazolines, e.g., I, to be obtained in high yields within short reaction times.  Aromatization of imidazolines was performed under microwave irradn. in toluene and using Magtrieve as the oxidant to give imidazoles, e.g., II, in good yields.  The X-ray structures for five of these derivs. are also provided.  In all cases, the mols. were assembled into chains through N-H···N hydrogen bonds. – Tetrahedron (2006) vol. 62 (25) pp. 5868-5874

Recyclable supported catalysts in microwave-assisted reactions: first Diels-Alder cycloaddition of a triazole ring

Angel Diaz-Ortiz, Cozar De, Pilar Prieto, Antonio de la Hoz, Andres Moreno. The authors describe here the first example in which a 1,2,3-triazole ring acts as a diene towards DMAD in microwave-assisted solvent-free Diels-Alder cycloaddns.  The extrusion of a mol. of a nitrile affords pyrazole derivs. as the products.  The yields can be markedly increased by using a recyclable supported Lewis acid catalyst, which can be reused at least five times without a decrease in the yield. – Tetrahedron Letters (2006) vol. 47 (49) pp. 8761-8764

Selectivity under the action of microwave irradiation Antonio de la Hoz, Angel Diaz-Ortiz, Andres Moreno. A review.  – Microwaves Org. Synth. (2nd Ed.) (2006) vol. 1 pp. 219-277

Microwave irradiation as an efficient tool for the generation of N-heterocyclic ortho-quinodimethanes: synthesis of polyheterocyclic compounds by Diels-Alder reactions

Angel Diaz-Ortiz, Maria Herrero, Antonio de la Hoz, Andres Moreno, Jose Carrillo. Microwave irradn. provides a general methodol. for the generation of ortho-quinodimethanes derived from 1,2,4-triazine, pyrazole, and 1,2,3-triazole.  The cycloaddn. reactions of such compds. with electron-deficient dienophiles allow the corresponding heteropolycyclic adducts to be obtained within 15 min in 51-87% yield. – Synlett (2006) (4) pp. 579-582

A dendritic fullerene-porphyrin dyad

Stephane Campidelli, Robert Deschenaux, Angela Swartz, G Rahman, Dirk Guldi, Dragana Milic, Ester Vazquez, Maurizio Prato.

We describe the synthesis, characterization and photophysical properties of a fullerene derivative whose structure includes a Zn-porphyrin and a second generation liquid-crystalline (LC) dendrimer. The size of the fullerene and porphyrin units with respect to the size of the LC dendrimer prevents the formation of liquid-crystalline phases. However, this system gives interesting photoinduced electron transfer phenomena. Compound  has been investigated by steady state and time resolved fluorescence as well as transient absorption spectroscopy in polar and apolar solvents. We demonstrate that the fluorescence of the porphyrin unit in  is quenched compared to the Zn-tetraphenylporphyrin used as reference. Femto- and picosecond transient absorption permit to identify the formation of a radical ion pair while nanosecond experiments allowed the determination of the charge recombination lifetimes. – Photochem. Photobiol. Sci. (2006) vol. 5 (12) pp. 1137-1141

Liquid-Crystalline Bisadducts of [60]Fullerene

Stéphane Campidelli, Ester Vázquez, Dragana Milic, Julie Lenoble, Carmen Atienza Castellanos, Ginka Sarova, Dirk Guldi, Robert Deschenaux, Maurizio Prato. A second-generation cyanobiphenyl-based dendrimer was used as a liquid-crystalline promoter to synthesize mesomorphic bisadducts of [60]fullerene. Liquid-crystalline trans-2,trans-3, and equatorial bisadducts were obtained by condensation of the liquid-crystalline promoter, which carries a carboxylic acid function, with the corresponding bisaminofullerene derivatives. A monoadduct of fullerene was also prepared for comparative purposes. All the compounds gave rise to smectic A phases. An additional mesophase, which could not be identified, was observed for the trans-2 derivative. The supramolecular organization of the monoadduct derivative is governed by steric constraints. Indeed, for efficient space filling, adequacy between the cross-sectional areas of fullerene (100 Å2) and of the mesogenic groups (22−25 Å2 per mesogenic group) is required. As a consequence, the monoadduct forms a bilayered smectic A phase. The supramolecular organization of the bisadducts is essentially governed by the nature and structure of the mesogenic groups and dendritic core. Therefore, the bisadducts form monolayered smectic A phases. The title compounds are promising supramolecular materials as they combine the self-organizing behavior of liquid crystals with the properties of fullerene. The Journal of Organic Chemistry (2006) vol. 71 (20) pp. 7603-7610

 

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