Juan F. Piniella

Synthesis and 1,3-dipolar cycloadditions of a new enantiopure cyclic nitrone

Abstract A new enantiopure cyclic nitrone has been efficiently synthesized from a d -glyceraldehyde derivative. Its 1,3-dipolar cycloaddition to different classes of dipolarophiles show complete antifacial selectivity, furnishing highly functionalized enantiopure bicyclic isoxazolidines.

Preparation of enantiomers of 1-(1-naphthyl)-2,2-dimethylpropylamine and their behaviour as chiral solvating agents: study of diastereochemic association by Job's plots and intermolecular NOE measurements

Abstract Enantiomers of 1-(1-naphthyl)-2,2-dimethylpropylamine have been obtained and considered as chiral solvating agents against several compounds. The formed complexes have been studied with the aid of the nuclear Overhauser effect and its stoichiometry by the method of continuous variations. Two diastereoisomeric complexes present similar geometry of association by π–π-stacking of the aromatic rings and by hydrogen bonding of the functional groups.

Synthesis and structure of (4R,5R)-α,α,α′,α′-2,2-hexaphenyl-4,5-dimethanol-1,3-dioxolane

Abstract We report the synthesis of the 1,4-diol 2 (4R,5R)-α,α,α′,α′-2,2-hexaphenyl-4,5-dimethanol-1,3-dioxolane from dimethyl-L-tartrate and benzophenone. The X-ray and the IR structural studies on 2 show that this compound has a preferred conformation with OH⋯Ph interactions which are different from related compounds.

PROTECTED DERIVATIVES OF (R)-CYSTEINE AND (R)-CYSTEINOL

Abstract The synthesis of N, O, S protected forms of ( R )-cysteine and ( R )-cysteinol as bicyclic derivatives is described. The reactivity and the preparation of substituted derivatives of these systems is also discussed.

FIRST EXAMPLE OF A THIRD GENERATION NITRONE CYCLOADDITION

Abstract Compounds 5 and 6, derived from the cycloadditions of a nitrone to α,β-unsaturated lactones, were oxidized with m-chloroperbenzoic acid affording regiospecifically aldonitrones, 8 and 14, respectively. These second generation nitrones were reacted with several dipolarophiles yielding cycloadducts 9–13, 15, and 16. A repeated sequence of oxidation-cycloaddition applied to compound 12 allowed the isolation of the first example of a third generation cycloadduct, 17. During this work a series of new highly functionalized pyrrolidines have been prepared.

Photocycloaddition of (Z)-1,2-dichloroethylene to enantiopure 2(5H)-furanones: an efficient strategy for the diastereoselective synthesis of cyclobutane and cyclobutene derivatives

A highly stereoselective and efficient synthetic approach to cyclobutane and cyclobutene derivatives has been developed consisting of a [2+2] photochemical cycloaddition of chiral 2(5H)-furanones to (Z)-1,2-dichloroethylene followed by dihydrodehalogenation or dihaloelimination.

Crystal structure of new lanthanide diphosphates KLnP2O7·2 H2O (Ln = Gd, Tb, Yb)

Abstract Crystals of lanthanide diphosphates KLnP2O7 · 2 H2O [Ln = Gd, Tb, Yb] have been synthesized and investigated by single-crystal X-ray diffractometry. The three structures resulted to be isostructural within monoclinic space group P21/c, with unit cell parameters of a = 7.7522(2) Å, b = 10.6732(8) Å, c = 10.1375(7) Å, β = 93.308(5)°, V = 837.39(9) Å3 (KGdP2O7 · 2 H2O = (1)), a = 7.7380(6) Å, b = 10.6360(8) Å, c = 10.1060(7) Å, β = 93.283(6), V = 830.37(11) Å3 (KTbP2O7 · 2 H2O = (2)), a = 7.6791(3) Å, b = 10.4992(7) Å, c = 9.9554(9) Å, β = 93.214(6)°, V = 801.39(10) Å3 (KYbP2O7 · 2 H2O = (3)). The three-dimensional frameworks are made by zig-zag chains of KO9 irregular polyhedra down c, sharing vertices with LnO7 polyhedra and P2O7 units; intricate hydrogen bonding networks complete the arrays.

First synthesis of (+)-rengyolone and (+)- and (-)-menisdaurilide

Abstract The benzofuranone natural products (+)-rengyolone and (+)- and (−)-menisdaurilide have been synthesised for the first time from a common enantiopure cyclohexane building block derived from a monoketal of p-benzoquinone.

Crystal structure of a vivianite-type mineral: Mg-rich erythrite, (Co2.16Ni0.24Mg0.60)(AsO4)2 · 8 H2O

The crystal structure of erythrite from Bouzaer, south Morocco, was refined through single crystal X-ray diffraction data, within monoclinic space group C2/m, with the following unit cell constants: a = 10.187(1) Å, b = 13.470(1) Å, c = 4.755(1) Å, β = 104.971(2)°, V = 630.3(2) Å3. Transition metal and magnesium cations are randomly distributed over two special positions Me(1) and Me(2), making up single and dimerical octahedral groups, connected by (AsO4) tetrahedra groups, in order to form infinite sheets down b. Such sheets are held together within the three-dimensional framework owing to the presence of an intricate hydrogen bond network. An infrared spectrum was collected in order to achieve information on the HOH bending modes of the erythrite.

A NEW REACTION OF TETRABUTYLAMMONIUM CAMPHORSULFONATE WITH P4S10. SYNTHESIS AND CRYSTAL STRUCTURE OF THE FIRST CHIRAL TETRATHIOPHOSPHATE DERIVATIVE

Abstract Compound 5 has been synthesized in a good yield by reacting tetrabutylammonium camphorsulfonate with P4S10, and characterized by X ray diffraction.