Isabel Merino

One pot synthesis of 2-vinyl-1-azadienes and divinylketones

Abstract Preparation of 2-vinyl-1-azadienes and 1,4-pentadien-3-ones from N -phenyl-triphenyl-λ 5 -phospazene, triphenyl(prop-2-ynyl)phosphonium bromide and aldehydes is described.

Liquid chromatographie separation of penicillamine enantiomers derivatized with OPA/2-ME on aβ-cyclodextrin bonded phase

A high performance liquid Chromatographic method has been developed for the resolution of penicillamine enantiomers on a β-cyclodextrin (β-CD) column. Fluorogenic derivatives of the D,L-penicillamine were first formed by usingo-phthaldehyde/2-mercaptoethanol (OPA/2-ME) as derivatizating reagent. These chiral derivatives were then chromatographed on a commercially available chiral stationary phase of β-CD with 50/50 ethanol/1% triethylammonium acetate (pH 4.5) as a mobile phase, and detected fluorimetrically at 450 nm (λex = 355 nm). After careful optimization of the classical Chromatographic parameters good resolution was achieved between the d and l enantiomers. The method proposed here is simple and rapid and can detect the presence of 0.5% of the L-enantiomer in D-penicillamine pharmaceutical preparations (tablets).

A simple and efficient synthesis of 2-amino-1,3-butadienes from β-enamino phosphonium salts

Abstract A new and very simple synthesis of 2-amino-1,3-butadienes is described through Wittig reaction of the phosphoranes generated “in situ” from the β-enamino phosphonium salts with aldehydes.

Synthesis and structure of ruthenium(IV) complexes featuring N-heterocyclic ligands with an N-H group as the hydrogen-bond donor: hydrogen interactions in solution and in the solid state.

The synthesis and characterization of novel ruthenium(IV) complexes [Ru(η(3):η(3)-C(10)H(16))Cl(2)L] [L = 3-methylpyrazole (2b), 3,5-dimethylpyrazole (2c), 3-methyl-5-phenylpyrazole (2d), 2-(1H-pyrazol-5-yl)phenol (2e), 6-azauracile (3), and 1H-indazol-3-ol (4)] are reported. Complex 2e is converted to the chelated complex [Ru(η(3):η(3)-C(10)H(16))Cl(κ(2)-N,O-2-(1H-pyrazol-3-yl)phenoxy)] (5) by treatment with an excess of NaOH. All of the ligands feature N-H, O-H, or C═O as the potential hydrogen-bonding group. The structures of complexes 2a-2c, 2e, 3, and 5 in the solid state have been determined by X-ray diffraction. Complexes 2a-2c and 3, which contain the pyrazole N-H group, exhibit intra- and intermolecular hydrogen bonds with chloride ligands [N-H···Cl distances (Å): intramolecular, 2.30-2.78; intermolecular, 2.59-2.77]. Complexes 2e and 3 bearing respectively O-H and C═O groups also feature N-H···O interactions [intramolecular (2e), 2.27 Å; intermolecular (3), 2.00 Å]. Chelated complex 5, lacking the O-H group, only shows an intramolecular N-H···Cl hydrogen bonding of 2.42 Å. The structure of complex 3, which turns out to be a dimer in the solid state through a double intermolecular N-H···O hydrogen bonding, has also been investigated in solution (CD(2)Cl(2)) by NMR diffusion studies. Diffusion-ordered spectroscopy experiments reveal an equilibrium between monomer and dimer species in solution whose extension depends on the temperature, concentration, and coordinating properties of the solvent. Preliminary catalytic studies show that complex 3 is highly active in the redox isomerization of the allylic alcohols in an aqueous medium under very mild reaction conditions (35 °C) and in the absence of a base.

Stereoselective Syntheses of Allylic Amines Through Reduction of 1-Azadiene Intermediates

Abstract The stereoselective synthesis of primary and secondary E-allylic amines by reduction of 1-azadiene intermediates is described. β-Enamino phosphonium salts are suitable starting materials to prepare secondary allylic amines. Two methods are reported for the obtention of primary allylic amines from 4-amino-1-aza-1,3-dienes. Method A leads to the desired compounds by straight reduction with AlH3 or DIBALH; method B is a stepwise procedure that allows for better yields when sterically hindered 4-amino-1-aza-1,3-dienes are employed.

Synthesis and reactions of β-enamino phosphonium salts. Preparation of 2-vinyl-1-aza-1,3-dienes and penta-l,4-dien-3-ones

Reaction of N,P,P,P-tetraphenyl-λ5-phosphazene 1 and prop-2-ynyltriphenylphosphonium bromide 2 followed by addition of aliphatic, heteroaromatic and aromatic aldehydes leads to β-enamino phosphonium salts 7, while substituted tetrahydropyridines 9 are obtained when α,β-unsaturated aldehydes are used. Functionalized phosphonium salts 7 are precursors of Wittig reagents and act as intermediates in the synthesis of 2-vinyl-1-aza-1,3-dienes 11 and penta-l,4-dien-3-ones 12.

Nucleophilic Additions to Coordinated 1,10-Phenanthroline: Intramolecular, Intermolecular, Reversible, and Irreversible

KN(SiMe3 )2 reacts with [Re(CO)3 (phen)(PMe3 )]OTf via reversible addition to the phen ligand and irreversible deprotonation of the PMe3 ligand followed by intramolecular attack to phen by the deprotonated phosphane, whereas MeLi irreversibly adds to phen. The addition of MeLi has been shown to be intermolecular, unlike previously known nucleophilic additions to pyridines.