Dearomatizing anionic cyclization of N-methyl-N-benzyldi(1-naphthyl)phosphinamide: a route for access to a new class of functionalized tricyclic azaphospholes with antitumor properties

The dearomatizing anionic cyclization of N-alkyl-N-benzyldi(1-naphthyl)phosphinamide 1d followed by trapping with a series of carbonyl reagents and α,β-unsaturated ketones under optimized conditions provided new tetrahydro-1H-naphtho[1,2-c][1,2]-azaphosphole 1-oxides from moderate to high yields and diastereoselectivities. In addition, two doubly dearomatized compounds as a result of double dearomatization on the two naphthalene rings of 1d have been isolated at first time. Three functionalized azaphospholes have been evaluated on three different human tumor cell lines showing growth inhibition factors (GI₅₀) at a micromolar scale. One of these heterocycles has also shown cytostatic properties.     

Acid-catalysed,nucleophile-catalysed and thermal decomposition of 2-amino-3-(2′,2′-dimethylaziridino)-1,4-naphthoquinone

The course of the thermal, acid-catalysed and iodide-catalysed decomposition of 2-amino-3-(2′,2′-dimethylaziridino)-1,4-naphthoquinone (III) was investigated. Thermal and iodide-catalysed decompositions gave mainly 2,3-diamino-1,4-naphthoquinone (VI) and 2-amino-3-(2′-methylallylamino)-1,4-naphthoquinone (V) together with low amounts of 2,2-dimethyl-1,2,3,4,5,10-hexahydrobenzo[g]quinoxaline (IV) and 2-isopropyl-1H-naphthoimid-azole-4,9-dione (VII). The acid catalysed isomerization of the aziridinonaphthoquinone III with halohydric acids or with acetic acid readily gave the opening of the aziridine ring; the corresponding salts of 2-amino-3-(2′-haloisobutylamino)-1,4-naphthoquinones (VIIIa-c) and 2-amino-3-(2′-acetoxyisobutylamino)-1,4-naphthoqunone (X) were formed by cleavage of the carbon-nitrogen bond at the substituted carbon atom. Hypotheses on the mechanism of these reactions are given.     

Electrodeposited Pt-Ir electrodes: characterization and electrocatalytic activity for the reduction of the nitrate ion

The activity of Pt-Ir deposits on titanium for the reduction of the nitrate ion in 0.5 M perchloric acid was studied. The electrodes were characterized by SEM-EDAX, XPS and cyclic voltammetry. The activity of the electrodes for the nitrate reduction depended on the Pt-Ir ratio. Repetitive cyclic voltammograms produced an enrichment of the electrode surface with Ir and a decrease of the catalytic activity. A synergistic effect in the electrodes with low iridium content is discussed. Received: 2 June 1997 / Accepted: 28 August 1997     

An effective one-pot synthesis of 5-substituted tetronic acids

An expeditious one-pot synthesis of 5-substituted tetronic acids from aldehydes and terminal conjugated alkyne as starting materials is described. The entire process embodies two consecutive chemical events: a catalytic domino reaction to build the 1,3-dioxolane scaffolds 5 and a two-step acid-catalyzed trans-acetalization-lactonization reaction to furnish the tetronic acid derivatives 6.     

Variable strategy toward carbasugars and relatives. 5.(1) Focus on preparation of chiral nonracemic medium-sized carbocycles

The feasibility of sequential vinylogous aldol (intermolecular)/silylative aldol (intramolecular) addition reactions involving furan- and pyrrole-based dienoxysilanes, 6 and 12, in the synthesis of carbasugar frameworks is illustrated by the preparation of the scantily investigated carbaseptanose and carbaoctanose representatives of this class of compounds. The target compounds, 1, 2, 3, ent-2, ent-3, and 4, were obtained from readily available carbohydrate precursors (5 and 19) in yields of 21-30% over 8-12 steps. The irreversible silylative ring-closing aldolisation of gamma-substituted dihydro-5H-furan-2-one and pyrrolidin-2-one aldehydes (9, 16, ent-16, and 22) driven by the TBSOTf/Pr(i)(2)EtN Lewis acid-Lewis base couple was shown to be a practical, diastereoselective maneuver to forge the densely functionalized, medium-sized core carbocycles.     

Synthesis and X‐Ray Single Crystal Structure of Two New Copper Complexes with the Redox Active Ligand 1,10‐Phenanthroline‐5,6‐dione

The synthesis and the crystal structures of the complexes [Cu(L^I)₂](ClO₄) ( 1 ) and [Cu(L^I)(CH₃CN)₂(ClO₄)₂] ( 2 ) are reported. 1 crystallizes in the monoclinic space group C2/c with the unit cell dimensions a = 13.169(4), b = 12.289(3), c = 14.732(3) Å, β = 109.03(2)° and Z = 4. Copper(I) is coordinated to four N atoms of the two 1,10‐Phenanthroline‐5,6‐dione (L^I) ligands with a two‐fold axis passing between the ligands. The copper(II) compound 2 crystallizes in the orthorhombic space group Pbn2₁ with unit cell dimensions of a = 7.498(5), b = 23.492(7), c = 12.363(4) Å and Z = 4. Copper(II) coordination can be described as a distorted octahedron with the N donor atoms of one L^I ligand and of two molecules of CH₃CN occupying the equatorial positions completed by two oxygen atoms of the two perchlorate molecules in the axial positions.     

Hydrogenation of citral on Ir/SiO2 catalysts. Effect of the addition of Nb2O5 on surface and catalytic properties

Hydrogenation of citral over Ir supported on SiO₂, Nb₂O₅ and Ir/Nb₂O₅-SiO₂ catalysts reduced at 473 K (LT) and 773 K (HT) was studied. High selectivity to unsaturated alcohol was found, the main reaction products being geraniol and nerol. The LT catalysts show higher conversion levels, the one with a higher Nb content displays highest conversion.     

Total stereoselective synthesis of (+)-goniothalesdiol

[reaction: see text] The stereoselective synthesis of (+)-goniothalesdiol (1) was accomplished in nine steps starting from commercially available (-)-(2S,3S)-dimethyl D-tartrate (3). The key features were a completely diastereoselective reduction of a beta-ketosulfoxide to generate the stereogenic center at C-5 in 7 and formation of the 2,5-cis-substituted tetrahydrofuran ring in 10 from a stereoselective Et(3)SiH/TMSOTf-promoted reductive cyclization/deoxygenation.     

Interpolated potential energy surface for abstraction and exchange reactions of NH 3 + H and deuterated analogues

An ab initio interpolated potential energy surface for the hydrogen abstraction and exchange reactions between ammonia and a hydrogen atom is reported. The interpolation is constructed over a set of data points calculated at the unrestricted coupled cluster approximation, using single and double excitations, and including the triple excitations non-iteratively. New data point selection methods were used to improve the convergence and accuracy of the interpolated surface.