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11.
Paolesse R Nardis S Venanzi M Mastroianni M Russo M Fronczek FR Vicente MG 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(5):1192-1197
5,10,15-Triphenylcorrole (1) reacts with the Vilsmeier reagent (POCl(3)/DMF) to give the corresponding 3-formyl derivative 3 as the major product. The regioselectivity of the reaction was proven by X-ray crystallography and only traces of the 2-formyl isomer were observed. A more polar product is also observed and this compound becomes the major product when an excess of DMF is used for the preparation of the Vilsmeier reagent, while the formation of the 3-formyl isomer is almost completely suppressed. X-ray crystallography allowed us to identify this compound as the fully substituted N-ethane bridged derivative 4, formed from the attack of the Vilsmeier reagent at the inner core of the macrocycle. This compound is unique among porphyrinoid macrocycles, and further confirms the peculiarity of corrole chemistry. 相似文献
12.
Paolesse R Monti D La Monica L Venanzi M Froiio A Nardis S Di Natale C Martinelli E D'Amico A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(11):2476-2483
Porphyrin diad 1 was synthesized by reaction of the acyl chloride of porphyrin 2 and trans-1,2-dithiane-4,5-diol. The Co complex of this diad was studied as a potential enantioselective receptor for chiral recognition in solution and in the solid state. In solution both enantiomers of limonene induce significant changes in the visible and circular dichroism (CD) spectra of [Co2(1)], while a different behavior is observed in the case of the enantiomeric pair of trans-1,2-diaminocyclohexane. A different efficiency of [Co2(1)] chiral recognition is obtained for these compounds, with a remarkable degree of enantiodiscrimination observed in the case of limonene. Self-assembled monolayers of [Co2(1)] were deposited onto the gold electrodes of quartz crystal microbalances to be used as sensing materials of nanogravimetric sensors operating in the gas phase. The enantiodiscrimination properties of these sensors towards the enantiomeric pairs of chiral analytes have been studied. While in the case of analytes bearing donor ligand atoms we did not observe a remarkable enantioselectivity, a significant degree of chiral discrimination was observed in the case of limonene; this result is particularly encouraging for the potential development of enantioselective chemical sensors for use in an array configuration. 相似文献
13.
A novel pyridinium salt photoelectrocyclization-nucleophilic bicyclic aziridine ring opening reaction sequence has been investigated in order to determine its preparative potential. N-Alkylpyridinium perchlorates were found to undergo photoinduced electrocyclization upon irradiation in nucleophilic solvents, such as H(2)O and MeOH, to efficiently produce 6-alkyl-6-azabicyclo[3.1.0]hex-2-en-4-yl alcohols and ethers. The bicyclic aziridine photoproducts react with a number of different nucleophiles (e.g., H(2)O, MeOH, AcOH, AcSH) under acid-catalyzed conditions to produce 5-(nucleophile-substituted)-4-(alkylamino)cyclopenten-3-yl alcohols and ethers. The aziridine ring opening processes are both regioselective and stereoselective, yielding trans,trans-trisubstituted cyclopentenes exclusively, apparently as a consequence of the operation of an SN(2) mechanism. The effects of C-alkyl substitution on the regiochemistry of the pyridinium cation photocyclization reaction were briefly probed, and a method was developed to produce trans,cis-trisubstituted cyclopentenes by use of this tandem preparative sequence. 相似文献
14.
A synthetic strategy for the preparation of cyclic peptide mimetics based on SET-promoted photocyclization processes 总被引:2,自引:0,他引:2
Yoon UC Jin YX Oh SW Park CH Park JH Campana CF Cai X Duesler EN Mariano PS 《Journal of the American Chemical Society》2003,125(35):10664-10671
A novel method for the synthesis of cyclic peptide analogues has been developed. The general approach relies on the use of SET-promoted photocyclization reactions of peptides that contain N-terminal phthalimides as light absorbing electron acceptor moieties and C-terminal alpha-amidosilane or alpha-amidocarboxylate centers. Prototypical substrates are prepared by coupling preformed peptides with the acid chloride of N-phthalimidoglycine. Irradiation of these substrates results in the generation of cyclic peptide analogues in modest to good yields. The chemical efficiencies of these processes are not significantly affected by (1) the lengths of the peptide chains separating the phthalimide and alpha-amidosilane or alpha-amidocarboxylate centers and (2) the nature of the penultimate cation radical alpha-heterolytic fragmentation process (i.e., desilylation vs decarboxylation). An evaluation of the effects of N-alkyl substitution on the amide residues in the peptide chain showed that N-alkyl substitution does not have a major impact on the efficiencies of the photocyclization reactions but that it profoundly increases the stability of the cyclic peptide. 相似文献
15.
M. Pilar Gamasa Mariano Laguna Daniel Miguel Víctor Riera 《Transition Metal Chemistry》1981,6(6):374-376
Summary Bidentate ligands can readily replace acetone in thefac-[Mn(CO)3(chel)(OCMe2)]+ complexes or the perchlorate group fromfac-[Mn(CO)3(chel)(OClO3)] yieldingfac-[Mn(CO)3(chel)(L-L)]+ or [{fac-Mn(CO)3(chel)}2(L-L)]2+ [chel = 1,10-phenanthroline (phen), 2,2-bipyridine (bipy), 1,2-bis(diphenylphosphine)ethane (dpe); L-L = bis(diphenylphosphine)methane (dpm), dpe, 1,4-bis(diphenylphosphine)butane (dpb), succinonitrile (suc), and glutaronitrile (glu)]. Some of these mononuclear complexes are precursors for binuclear complexes which are linked by bridging phosphines or nitriles. 相似文献
16.
Patrick S. Mariano George I. Glover Timothy J. Wilkinson 《Photochemistry and photobiology》1976,23(3):155-161
Abstract— Results of a quantitative photochemical study of poly- p -benzoylphenylacetimido-bovine serum albumin in the presence of small-molecule triplet quenchers are reported. The efficiency of quenching by organic salts containing low triplet energy chromophores is shown to be qualitatively dependent on their predicted association constants to the modified protein. In addition, quenching is inhibited by salts of organic acids which possess high binding affinities for the protein but do not contain chromophores of low triplet energy. Quantitative treatment of the quenching and inhibition data yields results which strongly support the operation of an 'affinity controlled' mechanism for triplet energy transfer from the benzophenone moieties of the modified-bovine serum albumin to quenchers such as α-naphthylacetate and trans -cinnamate. 相似文献
17.
Maria Grazia Bonicelli Gianfranco Ceccaroni Franco Gauzzi Giuseppe Mariano 《Thermochimica Acta》2005,430(1-2):95-99
Differential scanning calorimetry (DSC) and particle size measurements were carried out on disproportionation products of pure SnO to investigate the fusion and solidification behaviour of Sn droplets and their catalytic nucleation on Sn oxides. If disproportionation reaction takes place at T ≥ 798 K, the products are metallic Sn and SnO2; but for 523 < T < 798 K, SnO2 is replaced by an intermediate oxide (IO) SnxO(1+x). On melting, samples with IO show a drop of melting point of metallic tin due to Gibbs–Thomson effect; no lowering of melting point was observed in samples with SnO2. On the other hand, if solidification occurs in the presence of IO, Tin droplets always displayed three distinct exothermic solidification peaks, but if it takes place in the presence of SnO2, only one exothermic peak is observed. Undercooling values and contact angles were determined for each of the heterogeneous nucleation processes. The different behaviour of metallic Tin droplets was related to the different lattice symmetry of SnO2 and IO, which act as nucleation catalysts. 相似文献
18.
Estela M. Alvarez Patricia H. Risso Carlos A. Gatti Martín S. Armesto Mariano Burgos Verónica M. Relling 《Colloid and polymer science》2006,284(9):1016-1023
Colloidal casein aggregates (CCA) prepared from soluble whole bovine caseinates in the presence of Ca2+ and phosphate (Pi) ions by addition of different citrate (Cit) concentrations showed different mineral and proteic composition. Citrate concentration conditions the Ca and Pi concentrations incorporated into CCA, probably due to the complexing effect of this anion on calcium. A significant change in the incorporated Ca/Pi ratio at 8 mM citrate could very likely be associated to changes in CCA net charge. The incorporation of individual caseins to the colloidal particles obtained, as well as their average size and size distribution, depended also on the Cit concentration used [Cit]P. αS- and β-caseins assembled in the CCA structure sharply decreased at a [Cit]P higher than 15 mM, i.e., at a low Ca2+ concentration in the aggregates, showing that the presence of this cation is necessary for the incorporation of these caseins. An inverse relationship between the aggregation step rate in CCA enzymic coagulation and their average size was observed. The aggregation rate vs the average size curve obtained at [Cit]P 8 mM clearly differed from the curves obtained at 10 and 12 mM, respectively, a fact probably related to a change in the CCA net charge. This behavior showed the effect of citrate concentration on CCA functional properties. 相似文献
19.
20.
Enzo Barberio Mariano Daisy Aparecida do Nascimento Rebelatto 《The Journal of the Operational Research Society》2014,65(11):1664-1681
Although an essential condition for the occurrence of human development, economic growth is not always efficiently converted into quality of life by nation-states. Accordingly, the objective of this study is to measure the social efficiency—the ability of a nation-state to convert its produced wealth into quality of life—of a set of 101 countries. To achieve this goal, the Data Envelopment Analysis method was used in its standard, cross-multiplicative and inverted form, by means of a new approach called ‘triple index’. The main results indicated that the former Soviet republics and Eastern European countries stood out in terms of social efficiency. The developed countries, notwithstanding their high social indicators, did not excel in efficiency; however, the countries of south of Africa, despite having the worst social conditions, were also the most inefficient. 相似文献