Nicola Sardone

A FLUORESCENT CHEMOSENSOR FOR THE COPPER(II) ION

Abstract The two-component system anthracene-9-carboxylic acid 1,4,8,11-tetrathia-cyclotetradecan-6-ylester ( 1 ) has been synthesized, structurally characterized and investigated as a fluorescent chemosensor for the Cu 11 ion. Crystallographic details for 1 : space group P 2 1 / c with α = 9.894(2), b = 24.608(2), c = 10.759(2) A , α = 90, β = 105.88, γ = 90°; V = 2519.7 A 3 , Z = 4 (R = 0.088, R w = 0.066) . In ethanolic solution 1 selectively incorporates Cu 11 into its tetrathia crown component in the presence of other 3d metal ions and signals the recognition through the quenching of the fluorescence of the anthracene fragment. Quenching of the photo-excited state (which has a charge transfer nature) takes place through a photo-induced electron transfer from the fluorophore to the metal center and involves the Cu II /Cu I couple. The d 10 cation Ag 1 competes successfully with Cu 11 for the tetrathia cavity of 1 in an ethanolic solution (not in an acetonitrile solution), but the occurrence of the metal/receptor interaction cannot be signalled, due to the poor redox activity of the non-transition cation Ag 1 .

A new anhydrous amphibole from the Hoskins Mine, Grenfell, New South Wales, Australia; description and crystal structure of ungarettiite, NaNa 2 (Mn (super 2+) 2 Mn (super 3+) 3 )Si 8 O 22 O 2

Abstract Ungarettiite is a new amphibole species from the Hoskins mine, near Grenfell, New South Wales, Australia. It occurs with Mn-bearing oxides, silicates, and carbonates in a stratiform schist associated with metajasper, metabasalt, and metasiltstone. Ungarettiite is brittle, H = 6, Dmeas = 3.52 g/cm3, Dcalc = 3.45 g/cm3. In plane-polarized light, it is strongly pleochroic, X = orange red, Y ~ Z = very dark red; X Λ a = -2° (in β acute), Y = b, Z Λ C= 17° (in β obtuse), with absorption X < Y ≤ Z. Ungarettiite is biaxial positive, α = 1.717(2), β = 1.780(4), γ= 1.800(2); 2V= 51(2)°, dispersion r < ν. Ungarettiite is monoclinic, space group C2/m, a = 9.89(2), b = 18.04(3), c = 5.29(1) Å, β = 104.6(2)°, V = 912(1) Å3, Z = 2. The strongest ten X-ray diffraction lines in the powder pattern are [d(I, hkl )]: 2.176(10,171), 3.146(9,310), 2.544(9,2̅02), 1.447(9,3̅.11.1), 3.400(8,131), 1.656(8,461), 8.522(7,110), 2.299(7,1̅71), 2.575(6,241), and 2.047(6,202). Analysis by a combination of electron microprobe and crystal-structure refinement gives SiO2 50.66, Al2O3 0.04, TiO2 0.03, Fe2O3 0.50, FeO 0.00, Mn2O3 24.35, MnO 12.42, MgO 1.46, ZnO 0.10, CaO 0.18, Na2O 9.13, K2O 0.76, F not detected, sum 99.63 wt%. The formula unit calculated on the basis of 24 O atoms is (K0.15Na0.82)(Na1.97Ca0.03)(Mn2+1.66Mg0.34- Mn3+2.96Fe3+0.06Zn0.01)(Si7.99Al0.01)O2 and is close to the ideal end-member composition of NaNa2(Mn2+2Mn3+3)Si8O22O2. The crystal structure of ungarettiite was refined to an R index of ~ 1.5% using MoKα X-ray intensity data. Site-scattering refinement shows that the M1, M2, and M3 sites are occupied dominantly by Mn. The (M-O) distances are M1: 2.03; M2: 2.17; M3: 2.01 Å , compatible with the site occupancies M1~ M3 ~ Mn3+, M2 ~ Mn2+. All bonds to the O3 anion are very short, and a bond valence analysis indicates that the O3 site is occupied by a divalent anion: O2-, as suggested by the overall electroneutrality requirement of the structural formula.

Synthesis of enantiopure 3-hydroxymethylchromanes via intramolecular nitrone cycloaddition

Abstract Enantiopure ( R ) and ( S ) 3-hydroxymethylchromanes were prepared by the intramolecular nitrone cycloaddition strategy, starting from allyl-type ethers of 2-hydroxybenzaldehydes and using ( R )- N -( α -phenylethyl)hydroxylamine as chiral auxiliary.

A structurally characterized azide-bridged dinuclear nickel (II) cryptate

The macrobicyclic ligand L2 forms dimetallic NiII cryptate species in a delimited pH range, which are further able to include one N3-anion. The molecular structure of the azide-bridged complex shows an almost linear NiIINNNNiII arrangement and a different coordination at the two metal sites (one NiII being octahedral, the other trigonal bipyramidal).

Schiff-base template synthesis of tetra-aza macrocycles involving diethylmalonate as a padlock

Abstract Diethylmalonate acts as an efficient locking fragment in the Cu II directed synthesis of 14-membered tetra-aza-macrocycles. In the reaction of [Cu II (en) 2+ (en = 1,2-diaminoethane) with 2 equiv. of diethylmalonate in the presence of formaldehyde and triethylamine the 1,4,8,11-tetraazacyclotetradecane-6,6,13,13-tetracarboxylic acid tetraethyl ester copper(II) diperchlorate complex salt is formed: monoclinic, space group C 2/ c with a = 12.201(5) A , b = 12.464(5) A , c = 21.353(22) A , α = 90°, β = 91.30(6)°, γ = 90°, V = 3247(4) A 3 , and Z = 4 ( R = 0.072, R w = 0.072). The formaldehyde building block can be replaced by benzaldehyde in the same type of template procedure if the two en fragments are replaced by the tetra-amine 2.3.2-tet ( N/N′ -bis-(2-amino-ethyl)-propane-1,3-diamine) and if the synthesis is carried out under strictly anhydrous conditions. The 5,7-diphenyl-1,4,8,11-tetraazacyclotetradecane-6,6-dicarboxylic acid diethyl ester copper(II) diperchlorate complex is obtained in good yield and exhibits a regular square coordination which is not disturbed by the bulky phenyl substituents: triclinic, space group P 1 with a = 11.742(5) A , β = 16.949(8) A , c = 8.718(4) A , α = 101.15(4)°, β = 105.92(4)°, γ = 96.21(4)°, V = 1613(1) A 3 , and Z = 2 (R = 0.047, R w = 0.051) .

A new asymmetric approach towards 2-pyrrolidinones and pyrrolidines: Simple versus double stereodifferentiation

Abstract The condensation of a chiral 2-silyloxynole derivative with achiral and chiral formyl cation equivalents has been studied for the first time The methodology allows to build-up pyroglutamnnc aldehydes and piohnal systems with a steieocontrol from good lo excellent. Whereas the chiral auxiliary residing on the pyrrole system shows an intrinsic good level of diastereoface discrimination at C-5 the combined use of a 2-methoxy-3-tosyl-oxazolidine as a chiral formylatmg agent allows a total stereocontrol of the condensation A rationale for the observed stereochemical outcome is presented

Stereoselective synthesis of 6,5-bicyclic reverse-turn peptidomimetics

Abstract A flexible stereoselective synthetic scheme was developed to prepare 6,5-fused bicyclic lactams, that molecular mechanics calculations revealed to have a potential as reverse-turn mimetics. The convergence of the synthetic sequence was achieved by attachment of a properly substituted malonate unit to the (2S)-cis-5-(2-hydroxyethyl)proline tert-butyl ester. Stereoselective intramolecular alkylation of the malonate afforded the 6-membered lactam fused to the 2-carbalkoxy pyrrolidine nucleus. X-ray diffraction analysis of a more advanced synthetic derivative allowed the unequivocal assignment of the configuration at the newly created quaternary stereocenter as R.

Metal complexes of Imazapyr, a herbicide provided with efficient metal-chelating ability: crystal structure of the cobalt (III) and manganese (II) complexes

Abstract The complexes formed by the imidazolinone herbicide Imazapyr, (±)-2-(4-isopropyl-4-methyl-5-oxo-4,5-dihydro-I H -2-imidazol-2-yl)nicotinic acid (Imz) with Co(III), Mn(II), Co(II) and Ni(II) ions are described. The compounds [Co(Imz) 3 ]·3H 2 O and [Mn(Imz) 2 ]·2H 2 O were characterized by single-crystal X-ray analysis. [Co(Imz) 3 ]·3H 2 O crystallizes in the trigonal space group R -3 with a = b = 17.485(2), and c = 26.257(7) A, α = β = 90 and γ = 120°, Z = 6. The cobalt ion is hexa-coordinated, being surrounded by three bipylike chelating ligands. Noticeably, although Imazapyr acts as a mononegative anionic ligand, the imidazolinone moiety binds the metal through the lactam nitrogen. The finding supports an isomeric form for the Imazapyr(−1) anion where the lactam site is deprotonated. This feature is most probably imposed by the strong intramolecular bond between the imidazole and the carboxylate sites sharing a proton. [Mn(Imz) 2 ] · 2H 2 O crystallizes in the monoclinic space group P 2 1 / c with a = 10.584(5), b = 11.633(2), and c = 13.072(6) A, α = 90. β = 108.63(2) and γ = 120°, Z = 2. The structure consists of a polymeric three-dimensional network in which each metal ion is surrounded by two couples of nitrogen atoms belonging to two mutually trans ligands and two monodentate carboxylate groups from two further ligands. Each Imazapyr( = 1) anion acts as a bridging ligand in as much as it binds a metal ion through the bipy-like couple of pyridine and lactam nitrogens and another through the carboxylate group. Based on the specral properties, the Co(II) and Ni(II) derivatives adopt the same structure as [Mn(Imz) 2 ]·2H 2 O.

Periselectivity in the reactions of cyclopentadienones with 8-aryl-8-azaheptafulvenes

Abstract Periselectivity; Cycloadditions; Dienes; Trienes 8-Aryl-8-azaheptafulvenes 2 reacted smoothly with 2,5-dimethyl-3,4-diphenylcyclopentadienone (1a) to give exo [6+4] adducts, i.e. 4, as the dominant adducts along with minor amounts of endo [4+2] adducts, i.e. 7 and 8, and trace amounts of [8+2] adducts, i.e. 6. Passing from 2,5-dimethyl to 2,5-dimethoxycarbonyl-3,4-diphenylcyclopentadienone (1c) brought about an increase in reaction rate without any relevant change in selectivity. Structures of the exo [6+4] adducts 4 rest firmly on spectroscopic data and chemical behavior. Upon heating the [6+4] adducts 4 underwent a [3,3] aza-Cope rearrangement followed by [1,5-H] sigmatropic shifts to afford the [8+2] adducts 6. Mechanisms of formation of all the adducts are discussed. We conclude that only concerted cycloadditions are at work in the reactions of azaheptafulvenes with cyclopentadienones

Relative and absolute stereocontrol in intramolecular nitrone cycloadditions to the cyclohexene ring

Abstract The intramolecular reactivity of a nitrone derived from 2-(cyclohexen-3-yloxy)benzaldehyde has been investigated. By using (R)-α-phenylethylamine as chiral auxiliary, enantiomerically pure (9-amino-substituted) 1,2,3,4,4a,9a-hexahydro-9H-xanthen-1-ols were produced in satisfactory way.