Fluorescence-Labeled Pyrenesulfonamide Response for Characterizing Polymeric Interfaces in Composite Materials

E-glass fibers were silanized using a 1% (v/v) aqueous solution of -aminopropyltriethoxysilane (APES). Pyrene—sulfonamide conjugates were formed by reaction of 1-pyrenesulfonyl chloride (PSC) in acetonitrile (AcN), with the amine groups immobilized on the glass fiber surface. These pyrene—sulfonamide conjugates were used as fluorescence probes, being a relatively simple analytical method to study the coating microstructure of polyorganosiloxane layer on glass fibers. The first aim of this work was to estimate possible interactions of the polyaminosiloxane coating with surrounding molecules of different solvents (solvent accessibility to the chromophore). For this study, the fluorescence response of pyrene—sulfonamide dye (PSA) was correlated with solvent polarity parameters. It was concluded that all the studied solvents were accessible to the chromophore, and they can gather in two groups, depending on their ability to swell the poliorganosiloxane layer. The second objective was to estimate the rigidity of the coating polymer from the temperature dependence of PSA emission. At about 180 K, a sudden change in the behavior of different photophysical parameters of PSA were observed. This phenomenon was interpreted as a density change in the polyaminosiloxane attached to the glass fibers.     

Polymorphic screen and drug–excipient compatibility studies of the antichagasic benznidazole

The purpose of this study was to investigate the polymorphism and compatibility of benznidazole (BNZ), a drug used in the treatment of Chagas disease. This drug was subjected to a polymorphic screen using a number of solvents and precipitation procedures to explore the possible existence of different crystal structures of BNZ. The compatibility of BNZ with selected pharmaceutical excipients was evaluated in binary mixtures, in a ratio of 1:1 (w/w). These results were then analyzed with a variety of techniques, including differential scanning calorimetry, Fourier transform infrared spectroscopy, and X-ray powder diffractometry. No polymorphic forms of BNZ were detected despite some observed changes in the DSC profile. The thermal data indicate interaction of the drug with excipients hydroxyethylcellulose, polyethylene glycol, and hydroxypropyl-β-cyclodextrin. Additional studies using infrared spectroscopy confirm the incompatibility of BNZ with only the polyethylene glycol. This excipient should not be used in the development of solid dosage forms containing BNZ.     

REACTIONS WITH 2-THIOHYDANTOIN DERIVATIVES: SYNTHESIS OF MANNICH BASES AND IMIDAZOTHIAZOLE DERIVATIVES

Abstract

5-Arylidene-2-thiohydantoins (la-c) and 5-arylazo-1-phenyl-2-thiohydantoins (7a, b) were condensed with formaldehyde and primary or secondary aromatic amines to give the corresponding Mannich bases (2a-f) and (8a, b) respectively, which could also be converted into the educts (la-c) and (7a, b) by boiling in ethanolic HCI. On treatment of (2a-f), (5a-c) and (8a, b) with an ethereal diazomethane the colourless cyclopropane products (3a-c) and yellow N-methyl substituted compounds (9, b) were isolated respectively. Alkylation of (2d-f) with methyl iodide and (la-e) with 3-chloropentane-2,4 dione gave the corresponding 2-alkylmercapto derivatives (5a-c) and (2a-c) respectively, the former of which on hydrolysis by boiling ethanolic HCI afforded the hydantoin derivatives (6a-c). Cyclization of (12a-c) using polyphosphoric acid resulted in the formation of imidazothiazole derivatives (13a-c). The structure of the isolated products were established by elemental analyses and spectral data studies.