DMAP-catalyzed Efficient and Convenient Approach for the Synthesis of 3,3′-(Arylmethylene)bis(2-Hydroxynaphthalene-1,4-Dione) Derivatives

For the first time the 4-dimethylaminopyridine (DMAP) catalyzed straightforward and efficient procedure has been developed for the synthesis of 3,3′-(arylmethylene) bis(2-hydroxynaphthalene-1,4-dione) derivatives starting from lawsone (2-hydroxy-1,4-naphthoquinone) and a variety of (hetero)aromatic aldehydes in ethanol under microwave irradiation. Three of nine synthesized compounds are new. This method provides notable advantages over existing procedures including use of non-traditional basic catalyst and environmentally benign solvent, mild reaction conditions, excellent yields, short reaction time and simple workup.

SYNTHESIS OF POLYIMIDES OF ARILACYCLIC STRUCTURE

The article describes methods for producing polymeric materials based on tetra-carboxylic acid dianhydrides obtained by photochemical or solar irradiation from furan and maleic anhydride. The procedure of synthesis of aryl-alicyclic polyimides based on 7-оxsоdiciklo (2,2,1)-gepten -2,3- dicarboxylic acid(MAF) and diaminodiphenyl oxide diamines (DADFO) and dioxytriphenyldiamine (DOTFDA) in polar aprotic amide-type solvents has been studied in detail in the presence of a basic catalyst type: trimethyl-amine.The nature and reactivity of staring monomers affect the process of obtaining polyimides. The optimal conditions for obtaining polyimides with intrinsic viscosity values of 1.30-1.64 dl/g have been found. Physicochemical, electrical and thermal proper-ties of the synthesized polyimides have been investigated. It was found that they have increased elasticity, high tensile strength. Elongation at break of polyimide films reaches 30-43%, tensile strength is 130-180 MPa. According to their electrical properties, these polyimides are classified as medium-frequency dielectrics. In addition, they differ in thermoplasticity in the range from 210 ºС to 250 ºС, have thermal stability and do not decompose at heating in air to temperatures of 335-390 ºС, and the presence of oxide groups in the structure of polymers increases the solubility of polyimides.

Ketones as Electrophile in Nitroaldol Reaction: Synthesis of β,β-Disubstituted- 1,3‑dinitroalkanes and Allylic Nitro Compounds

β,β-Disubstituted-1,3-dinitro compounds were obtained exclusively with an overall yield of 83% through a domino nitroaldol/elimination/1,4-addition process, when excess nitromethane was added to cyclohexanone or butanone using DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), as a basic catalyst. On the other hand, β-nitroalcohols could be obtained in 30-84% yield, when nitromethane reacts with different aliphatic ketones in stoichiometric amounts, in the presence of catalytic amounts of K2CO3(s), Amberlyst®-A21 or TBAF.3H2O (tetra-n-butylammonium fluoride trihydrate)/THF (tetrahydrofuran). In addition, a new and versatile route to obtainment of allylic nitro compounds, by treatment of acetylated nitroalcohols and aldehydes in catalytic amounts of DBU or TBAF.3H2O, via a one-pot elimination/nitroaldol reaction sequence, was developed.

Control of Flexibility, Pore Structure and Hydrophobicity of Tetraethylorthosilicate/Methyltriethoxysilane Aerogels by Hybridization

The flexibility, pore structures and hydrophobicity could be controlled by changing TEOS/MTEOS ratio. A methyl functional group of MTEOS causes the difficulty of hydrolysis and condensation reactions, so that strong basic catalyst needs to be added for the gelation of MTEOS. Therefore, increasing of MTEOS ratio forms larger pore sizes and large primary particles with about one micrometer. MTEOS-based aerogels show the lowest specific area due to macropores with more than one thousand nanometers, although they are very flexible to elongate two times as long as their original sample length. For TEOS/MTEOS hybrid aerogels with 0.4–0.6 of TEOS ratio, they have the large specific surface area and pore volume, a little flexibility and hydrophobicity due to the remaining alkyl functional groups. This research presents the possibility of controlling flexibility, pore structures, hydrophobicity through hybridization of alkoxide and silane. It suggests a way of overcoming weaknesses of silica aerogels like brittleness and hydrophilicity.