The Complexation of Al^III, Pb^II, and Cu^II Metal Ions by Esculetin: A Spectroscopic and Theoretical Approach

UV–visible absorption spectroscopy combined with quantum chemical calculations and, notably, Time-Dependent Density Functional Theory were used to probe the structure of metal complexes with esculetin in dilute aqueous solution, at pH = 5. For the 1:1 complex formation, the studied metal ions can be classified according to their complexing power: aluminum­(III) > copper­(II) > lead­(II). For the three complexes, a chelate is formed with the fully deprotonated catechol moiety and an absorption band is observed at the same wavelength. In all cases, a pronounced ionic character is calculated for metal–ligand bonds. However, the complexes differ in their coordination sphere. Copper and lead are bound to two water molecules leading to a square plane geometry and a hemidirected complex, respectively, whereas aluminum atom has an octahedral environment involving three water molecules and a hydroxide ion. For Al^III only, a 2:1 complex is observed, and the involvement of an aluminum dimer was evidenced

Enhancement of the Water Solubility of Flavone Glycosides by Disruption of Molecular Planarity of the Aglycone Moiety

Enhancement of the water solubility by disruption of molecular planarity has recently been reviewed as a feasible approach in small-molecule drug discovery programs. We applied this strategy to some natural flavone glycosides, especially diosmin, a highly insoluble citroflavonoid prescribed as an oral phlebotropic drug. Disruption of planarity at the aglycone moiety by 3-bromination or chlorination afforded 3-bromo- and 3-chlorodiosmin, displaying a dramatic solubility increase compared with the parent compound

Cobalt-Catalyzed Vinylation of Aromatic Halides Using β‑Halostyrene: Experimental and DFT Studies

A new protocol for the direct cobalt-catalyzed vinylation of aryl halides using β-halostyrene has been developed in order to form functionalized stilbenes. A variety of aromatic halides featuring different reactive group were employed. This method proceeded smoothly with a total retention of the double bond configuration in the presence of triphenylphosphine as ligand. Preliminary DFT calculations rationnalize these results and proposed a reaction pathway in agreement with the experimental conditions. This procedure offers a new route to the stereoselective synthesis of stilbenes

Enantioselective Organocatalytic Partial Transfer Hydrogenation of Lactone-Fused Quinolines

The first enantioselective synthesis of 4-aza-podophyllotoxin derivatives by partial transfer hydrogenation of lactone-fused quinolines was achieved using a chiral Brønsted acid catalyst. This reaction was extended to a large scope of substrates with good yields and enantioselectivities