Houcine Ammar

Structural analysis of alfa grass (Stipa tenacissima L.) lignin obtained by acetic acid/formic acid delignification.

Alfa grass lignin obtained by the acetic acid/formic acid/water CIMV pulping process was characterized by FTIR and (1)H, (13)C-(1)H 2D HSQC, and (31)P NMR spectroscopies. Lignin samples purified by further dissolution/precipitation or basic hydrolysis steps were also analyzed. The CIMV alfa lignin is a mixture of low molar mass compounds (M(n) = 1500 g/mol) of SGH type with β-O-4 ether bonds as the major interunit linkage. The crude lignin contains fatty acids and residual polysaccharides. It also contains large amounts of acetate and hydroxycinnamates, mostly in the γ-position of β-O-4 interunit linkages. Although partial acetylation induced by the process cannot be excluded, the absence of aromatic acetates and acetylated polysaccharides in crude lignin demonstrates the mildness of the process. By combining smooth alkaline hydrolysis and dissolution/precipitation steps to the CIMV pulping, it is possible to produce a purified lignin with a composition and a structure quite analogous to that of the native polymer in the plant.

UV/vis absorption and fluorescence spectroscopic study of novel symmetrical biscoumarin dyes

Abstract The optical properties of six new 3,3′-phenylenebiscoumarin dyes, differing by the substitution pattern of the central phenyl group and by the presence of methoxy substituents, were investigated in CH 2 Cl 2 by UV/vis absorption and fluorescence spectroscopy. The spectroscopic behaviour of one of the dyes was also analysed in five other solvents. By comparison with monocoumarins, the absorption and emission spectra of the biscoumarin derivatives were shifted to high wavelengths. Most of them displayed high fluorescence quantum yields (0.7–0.8) and lifetimes in the nanosecond range, which can make these dyes very useful as new fluorescent probes.

Synthesis of New bis-Iminocoumarins by Schmidt Reaction Catalyzed by Ion-Exchange Resins

Abstract A new synthetic route to bis-iminocoumarins is proposed which involves the synthesis of iminocoumarins from reaction of 2-hydroxybenzaldehydes with arylacetonitriles and their coupling with aromatic diamines. Ion-exchange resins were used as catalysts in both steps of this synthesis. The reaction parameters were varied and obtained using Amberlyst 15 resin in cyclohexane at 80°C.

Small Iminocoumarin Derivatives as Red Emitters: From Biological Imaging to Highly Photoluminescent Non‐doped Micro‐ and Nanofibres

The fluorescence properties of four derivatives of 3-thienyl-2-(N-dicyanovinyl)iminocoumarin, bearing a diethylamino group in the 7-position or a methoxy group in the 6, 7 and 8 positions, were compared in solution and in the solid state. The 7-diethylamino derivative was strongly fluorescent in various solvents, with marked solvatochromism. Its fluorescence was quenched by aggregation. In contrast, the methoxy derivatives were only moderately or weakly fluorescent in solution, but two of them were strongly photoluminescent in the crystalline state, owing to favourable molecular packing. The 6-methoxy derivative even exhibited spectacular crystallization-enhanced emission, examples of which are particularly rare for this type of dyes. Dyes were tested for biological use. The 7-diethylamino derivative led to particularly strong fluorescence staining of the cytoplasm of HCT-116 colon cancer cells. No fading was observed over prolonged illumination by the microscope light beam, but a phototoxic effect was detected. The use of the dyes as red-emitting materials was also investigated. Using easy-to-implement preparation methods, the compounds self- assembled to give one-dimensional nano- and microsized particles, including millimeter-long microfibres that exhibited clear wave-guiding properties. This study shows the value of these low molecular-weight molecules for the preparation of new orange and red-emitting fluorescent materials based on totally pure dye.

Synthesis of Primary Amines by One-Pot Reductive Amination of Aldehydes

Abstract We report here a novel, one-pot, two-step reductive amination of aldehydes for the atom-economical synthesis of primary amines. The amination step has been carried out with hydroxylammonium chloride and does not require the use of a base. In the subsequent reduction step, a metal zinc/hydrochloride acid system has been used. This method is applicable to both aliphatic and aromatic aldehydes. The operational simplicity, the short reaction times, and the mild reaction conditions add to the value of this method as a practical alternative to the reductive amination of aldehydes. Supplemental materials are available for this article. Go to the publishers online edition of Synthetic Communications® to view the free supplemental file. GRAPHICAL ABSTRACT

Simple, Efficient Procedure for the Synthesis of Benzopyrano[2,3-c]isoxazoles

Abstract Synthesis of 3-imino-benzopyrano[2,3-c]isoxazoles was successfully performed using heterorocyclization of 2-imino-2H-1-benzopyrano 3-carbonitrile derivatives with hydroxylamine. The synthesized compounds were characterized by infrared, 1H NMR, 13C NMR, mass spectroscopy, and elemental analysis. GRAPHICAL ABSTRACT

Synthesis of 2-Amino-4-(2-hydroxynaphthyl)-4H-chromene-3-carbonitriles by Michael Addition and Their Transformation into New Pentacyclic Compounds

Abstract 2-Amino-4-(2-hydroxynaphthyl)-4H-chromene-3-carbonitriles were synthesized by Michael addition of various 3-cyanoiminocoumarins and β-naphthol in good yield. The heterocyclization of these materials in an acidic medium leads new heterocyclic compounds, which have not previously been described, in moderate to good yields and good selectivity. The synthesized compounds were characterized by infrared, 1H NMR, 13C NMR, two-dimensional NMR, and elemental analysis. GRAPHICAL ABSTRACT

Simple and convenient access to α,α,α-trisubstituted amides by double addition of Grignard reagents to acyl cyanohydrins

The double addition of Grignard (alkyl, aryl, alkenyl, alkynyl) reagents to acyl cyanohydrins was performed under unusually smooth conditions with a concomitant O-N acyl transfer, providing a very simple and general access to α,α,α-trisubstituted amides.

Synthesis of New Iminocoumarins Bearing Parabanic Moieties

Abstract The synthesis of novel substituted 3-p-nitro-phenyliminocoumarins and corresponding N-ureaiminocoumarins is described. The condensation of these materials with oxalyl chloride leads to the corresponding N-parabanic iminocoumarins, which have not previously been described, in moderate or good yields and high selectivity. The structures were characterized by Fourier transform infrared, 1H and 13C NMR, and elemental analysis.

Novel Synthesis of Bis-Iminocoumarins

Abstract Reaction of 3-aryl iminocoumarins with diacid chlorides as C-electrophilic reagents under mild conditions novel bis-iminocoumarins in good yields. When the reaction was performed with alkylene dibromides by heating them in toluene in the presence of IRA 900 resin, bis-ether compounds were obtained by way opening the pyranic ring. The structures of the product obtained were characterized by Fourier transform infrared, 1H NMR, 13C NMR, and elemental analysis. GRAPHICAL ABSTRACT