Tonino Caruso

Cs2CO3 Promoted coupling reactions for the preparation of skipped diynes

An improved methodology for the preparation of copper(I) alkynides has been developed using cesium carbonate as base. In the presence of cesium carbonate and CuI various 1-alkynes were converted smoothly to the corresponding copper alkynides which in situ reacted with propargylic halides in order to synthesize skipped diynes.

First total synthesis of natural aplyolides C and E, ichthyotoxic macrolides isolated from the skin of the marine mollusc Aplysia depilans ☆

A convergent pathway is described for the synthesis of the marine macrolides aplyolides C 4 and E 5. The key fragment 8 was prepared stereoselectively by Sharpless asymmetric dihydroxylation of eneyne 13.

Stacking interactions between adenines in oxidized oligonucleotides.

The effects of stacking interactions on the oxidation potentials of single strand oligonucleotides containing up to four consecutive adenines, alternated with thymines and cytosines in different sequences and ratios, have been determined by means of differential pulse voltammetry. Voltammetric measurements point toward the establishment in solution of structured oligonucleotide conformations, in which the nucleobases are well stacked altogether. Molecular dynamics simulations confirm that finding, indicating that single strands assume geometrical parameters characteristic of the B-DNA form. The analysis of the voltammetric signals in terms of a simple effective tight binding quantum model leads one to infer a robust set of parameters for treating hole transfer in one-electron-oxidized DNA containing adenines and thymines.

Improving methodology for the preparation of uracil derivatives from Fischer carbene complexes. Microwave activation

The effect of the microwave irradiation on the reaction of alkynyl alkoxy carbene complexes with ureas is studied. The results show that the use of microwave activation could represent an alternative to the reaction in conventional conditions for the metal carbene complex chemistry. In particular, is noteworthy that the use of large amounts of solvents could be drastically reduced or even avoided and, in any case, reaction times were dramatically shortened.

Proton transfer in oxidized adenosine self-aggregates

The UV-vis and the IR spectra of derivativized adenosine in dichloromethane have been recorded during potentiostatic oxidation at an optically transparent thin layer electrode. Oxidized adenosine shows a broad Zundel like absorption extending from 2800 up to 3600 cm(-1), indicating that a proton transfer process is occurring. Theoretical computations predict that proton transfer is indeed favored in oxidized 1:1 self-association complexes and allow to assign all the observed transient spectroscopic signals.

First total synthesis of natural aplyolides B and D, ichthyotoxic macrolides isolated from the skin of the marine mollusk Aplysia depilans☆

A convergent pathway is described for the synthesis of the marine macrolides aplyolides B (2) and D (3). Stereoselective preparation of a key fragment was achieved by Sharpless asymmetric dihydroxylation of eneyne 10.

Delocalized hole domains in Guanine-rich DNA oligonucleotides.

Differential pulse voltammetries of guanine-rich single- and double-stranded oligonucleotides containing up to six consecutive guanines are reported. The observed progressive lowering of the first voltammetric peak potential as the number of adjacent guanines increases unambiguously points toward the establishment of delocalized hole domains; the hole stabilization energy is ca. 0.1 eV per GG step, significantly lower than that observed for AA steps.

Modeling of radionuclides in natural fluids: synthesis and characterization of the Na4(UO2)2(OH)4(C2O4)2 complex

Abstract The coordination chemistry of dioxouranium(VI) with organic ligands may represent an useful model to describe the migration of radionuclides in natural fluids. A new dioxouranium(VI) ternary complex of formula Na 4 (UO 2 ) 2 (OH) 4 (C 2 O 4 ) 2 was precipitated at pH≅8. It was characterized by elemental analysis, ICP and IR spectroscopy, thermogravimetry (TG) and coupled TG–IR evolved gas analysis. Potentiometric measurements in the solution suggest that the equilibrium shifts from the prevalence of the (UO 2 ) 2 (OH) 2 (C 2 O 4 ) 4 6− complex to the [(UO 2 ) 2 (OH) 4 (C 2 O 4 ) 2 ] 4− complex before the formation of a solid phase.

Methyl and phenyl substituent effects on the catalytic behavior of NHC ruthenium complexes

New second-generation ruthenium benzylidene and isopropoxybenzylidene catalysts bearing N-heterocyclic carbene (NHC) ligands with o-biphenyl groups at the N-atoms and syn methyl or phenyl groups on the backbone were obtained and their catalytic behaviors were compared to those of analogous N-o-tolyl catalysts in standard ring-closing metathesis (RCM) reactions. A pronounced difference in catalyst efficiency was observed depending on the nature of ortho-N-aryl substituents (methyl or phenyl). Notably, very impressive catalytic performances were exhibited by N-o-biphenyl complexes with a syn dimethyl backbone in the formation of di- and trisubstituted cycloalkenes. To rationalize catalytic results, methyl and phenyl substituent effects on the steric and electronic properties of NHC ligands were assessed through experimental and theoretical investigations involving ruthenium complexes as well as newly developed rhodium derivatives. Despite the different electron donor capacities of the examined carbenes, the steric differences shown by N-o-biphenyl and N-o-tolyl NHCs, although subtle, were found to be the key factor in addressing catalyst behavior.

Synthesis of hyperbranched low molecular weight polyethylene oils by an iminopyridine nickel(II) catalyst

A 6-(2,6-dimethylphenyl)-2-(2,6-diisopropylphenyl)iminopyridine dibromo nickel(II) complex was synthesized, characterized by X-ray diffraction analysis and tested in ethylene polymerization using diethylaluminumchloride as the cocatalyst. Low molecular weight (Mn ∼ 103 g mol−1) polyethylene oils were obtained under a variety of reaction conditions. Detailed NMR analysis showed the formation of hyperbranched macromolecules (branching density >100 branches per 1000 carbons) with a high fraction of “branches on branch” and one unsaturation per chain, resulting in polymer features comparable to those of polymers produced by α-diimine Pd(II) catalysts. The DFT model of the catalytic species showed that the ortho-2,6-dimethylphenyl substituent of the pyridine group destabilizes the ethylene coordination to the metal centre but does not encumber both axial coordination site. So the polymerization performance of 1 can be addressed to the catalytic pocket generated by the coordinated ligand that favors both chain transfer and chain walking over propagation.