Papers by Keyword: Phenylacetylene

Abstract: An important liquid crystal intermediate of 4'-Bromoethynyl-4-pentyl-biphenyl was synthesized by bromo-reaction using N-bromosuccinimide as brominating agent, 4-Ethynyl-4'- pentyl-biphenyl as raw material, benzoyl peroxide (BPO) as catalyst and carbon tetrachloride (CCl₄) as reaction solvent. The effects of reaction variables were systematically optimized to achieve product with yield as high as possible. Under the optimal synthesis condition, where the temperature was 80oC, the mol ratio between 4-Ethynyl-4'- pentyl-biphenyl and NBS was 1:2, the weight rate of BPO to 4-Ethynyl-4'-pentyl-biphenyl was 2.5%, and the reaction time was 8 h, the product attained the best yield of 93.1%.

Abstract: Different Pd precursors were used to prepare Pd catalysts supported by using organic group modified silica. The catalysts were characterized by TEM and FTIR analysis. The results indicated that the small Pd nanoparticles (1-2nm) were achieved using Pd precursors with negative charge, while the size of Pd particle increased to 2-4 nm using Pd precursors with positive charge. For semihydrogenation of phenylacetylene, large-sized Pd partcles (2-4nm) exhibited high styrene selectivity compared with small-sized ones (1-2nm).

Abstract: Sonogashira coupling of phenylacetylenes with phenyl iodides in 1-butyl-3-methyl- imidazolium bromide (BMImBr) was explored. Using CuI/Pd(PPh3)4 as a catalyst and Im as the base, the expected substituted acetylenes were obtained with good to excellent yields (61%-95%) under mild conditions (4h, 60oC). After the product was isolated, the left ionic liquid can been readily recovered and reused in the subsquent runs with almost the same efficiency. The reactivity of different iodoarenes with terminal alkynes was also discussed.

Abstract: Novel catalytic systems based on PdZn alloys have been synthesized by polyol reduction over the entire compositional range [1, 2] and characterized by means of HRTEM, EDS and ICP. The expected bulk compositions were reproducible to within a 2 mol% margin and the purified particle suspensions stable for several months after preparation. The EDS results indicated the presence of considerable amounts of oxygen, especially in those samples containing high fractions of zinc. The particle size distributions were shown to be narrow and the mean sizes slightly decreased with higher molar fractions of palladium (diameter range 2.6 to 3.2 nm). In the catalytic hydrogenation of phenylacetylene, a strong dependence of the substrate conversion time on the Pd concentration was established, and selectivity towards the semihydrogenation product (styrene) was found to be close to 100 %. The selectivity dropped only shortly before the initial substrate was fully depleted.