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Telechelics by Polymer Chain Scission Reactions
Published in Eric J. Goethals, Telechelic Polymers: Synthesis and Applications, 2018
Ditelechelics of PVC-bearing peroxide functions are not prone to copolycondensation at temperatures equal or higher than 100°C due to poor thermal stability, but can be transformed into diacylchloride ditelechelics that allow the preparation of block copolycondensates.9 The chlorinating agent of choice is phosphorus pentachloride, since thionyl chloride induces a partial degradation of the polymeric substrate. This modification of the terminal functions can be done without significant change of the molecular weight. The diacylchloride telechelic can in turn be transformed into a dihydroxytelechelic by reaction with hydroxylamine.9 This compound can be used for further classical polycondensation. However, it is worth recalling here that the presence of peroxidized side groups due to the above synthesis greatly increases, after their reduction, the final functionality expressed as the number of hydroxylic functions per molecule. As a consequence, gelation instead of chain extension can be observed.
Self-assembling behaviour of new functional photosensitive cinnamoyl-based reactive mesogens
Published in Liquid Crystals, 2020
Alexej Bubnov, Martin Cigl, Nela Sedláčková, Damian Pociecha, Zuzana Böhmová, Věra Hamplová
4-hydroxybezoic acid (27.60 g, 0.20 mol) was dissolved in a mixture of sodium hydroxide (20.0 g, 0.50 mol) and water (300 ml) and cooled to 0°C. Then, methyl chloroformate (28.30 g, 0.30 mol) was added dropwise with stirring, keeping the temperature at 0°C. The reaction mixture was then stirred for ca. 2 h while a white precipitate was gradually formed. Resulting mixture was acidified by a small amount of hydrochloric acid (pH 4–5) and white solid was filtered off and washed with cold water. After drying, the solid was recrystallised from ethanol and dried under vacuum. Obtained 4-(methoxycarbonyloxy)benzoic acid was suspended in thionyl chloride (40 ml) and a catalytic amount of DMF was added. The reaction mixture was refluxed for 2 h. The excess of thionyl chloride was distilled off. Oily residue was diluted with toluene and the solvent removed on rotatory evaporator. Obtained benzoyl chloride 11 was used in the next synthetic step without further purification. 1H NMR (CDCl3): 8.18 (2H, d, J = 8.8, H-2, H-6), 7.37 (2H, d, J = 8.8, H-3, H-5), 3.96, (3H, s, OCH3).
The influence of flexible spacer and the chirality of the core on the formation of chiral nematic phase of symmetric dimers containing trifluoromethyl terminal
Published in Liquid Crystals, 2019
4-Ethoxybenzoic acid was obtained from Beili Chemicals (Suzhou) Co. Ltd. (Suzhou, Jiangsu, China). P-Dihydroxybenzene and sebacic acid were obtained from Tianjin Chemical Co. Ltd. (Tianjin, China). Thionyl chloride was obtained from Shenyang Xinxi Chemical Co. Ltd. (Shenyang, Liaoning, China). 4-(Trifluoromethyl) benzoic acid and 4′-hydroxy-4-biphenylcarboxylic acid were obtained from Sigma-Aldrich (Shanghai, China) without any further purification. 4,4′-Biphenyldiol was obtained from Sdyano Fine Chemical Co. Ltd. (Shijiazhuang, Hebei, China). (R,S)-1,2-Propanediol ((R,S)PD) and isosorbide (IB) were obtained from Chengdu Best-reagent Co. Ltd. (Chengdu, Sichuan, China). (R)-(−)-1,2-Propanediol ((R)PD) was obtained from Shanghai Meryer Chemical Technology Co. Ltd. (Shanghai, China). Tetrahydrofuran (THF) was dried over sodium metal and distilled. Pyridine was purified by distillation over KOH before using. Other analytical reagents are used as received.
Metal- and nonmetal-catalyzed synthesis of five-membered S,N-heterocycles
Published in Journal of Sulfur Chemistry, 2018
Navjeet Kaur, Nirmala Kumari Jangid, Vivek Sharma
2-Sulfenylchloro-benzoylchloride was obtained from 2-mercaptobenzoic acid in the classical method by the treatment of chlorine gas and thionyl chloride. Thereafter, respective benzoisothiazolones were afforded on quenching with primary amines [69–71]. In an alternative method, environmentally benign hypervalent iodine reagent [phenyl iodine(III)-bistrifluoroacetate] was utilized on 2-mercapto-N-aryl/alkylbenzamide substrates for the synthesis of S–N heterocycles. The synthesis of S–N heterocycles mainly depends on 2-mercaptobenzoic acid as depicted in the literature on benzoisothiazolones [72–75]. 2-Mercaptobenzoic acid is commercially available but its transformation into S–N-heterocycle involves corrosive and highly toxic reagents and/or multi-steps. Due to poor availability of substituted 2-mercaptobenzoic acid the synthesis of substituted aromatic S-N heterocycles has not been well documented. Therefore, the exploration of an environmentally benign and practical method for the synthesis of a diverse library of aryl benzoisothiazolones from readily available substrates is in demand. The allyl group possessing arylamides are also compatible with copper-catalyzed S–N coupling reaction. The synthesis of allyl bezoisothiazolone was difficult by the earlier known synthetic protocols. Allyl bezoisothiazolone was isolated in impure form by Grivas [76]. The unsuccessful synthesis of allyl benzoisothiazolone from N-allyl-2-mercaptobenzamide was reported with phenyliodine(III)-bistrifluoroacetate reagent (Scheme 4) [11,77].