Shiwei Lu

Selective formation of unsymmetric ureas by selenium-catalyzed oxidative-reductive carbonylation with CO

A series of unsymmetric ureas containing substituted groups have been synthesized via selenium-catalyzed selective oxidative-reductive carbonylation of amines and nitro compounds with CO instead of phosgene in one-pot reaction. These catalytic reactions are important from both synthetic and industrial points of view, because not only the reactions can be proceeded with high selectivity of higher than 99% towards desired unsymmetric ureas, but also there exists a phase-transfer process of the selenium catalyst in the reaction, so that the after-treatment of the catalysts and products from the reaction systems can be easily separated by simple phase separation

Dimerization of propylene by bis(β-ketiminate) nickel(II) and cobalt(II) catalysts in the presence of organoaluminum activator and phosphine ligand

A preliminary study of the catalytic behavior of bis(beta-ketiminate) nickel(ii) and cobalt(ii) complexes in the dimerization of propylene was undertaken in combination with organoaluminum co-catalyst and ancillary phosphine ligand. the effects of type and relative amounts of aluminum co-catalyst as well as the nature of nickel and cobalt precatalysts were investigated. the results showed that the presence of ancillary phosphine ligand deeply modified the activity and selectivity of catalytic system, especially at the reaction temperature below 0 degreesc. an extremely high turnover frequency up to 268,000 h(-1) and a rather hi-h selectivity to dimers (95.6%) by the bis(n-(2,6-dimethylphenyl)-4-aminopent-3-en-2-ono) nickel(ii) complex (1c) in the presence of et3al2cl3 and pcy3 was achieved in the propylene dimerization under appropriate reaction conditions. (c) 2003 elsevier science b.v. all rights reserved.

Selenium-catalyzed carbonylation of substituted nitrobenzenes with aminomethylpyrimidines as co-reagents to synthesize N-phenyl-N′-methylpyrimidylurea derivatives

Abstract A series of N -phenyl- N ′-methylpyrimidylurea derivatives have been synthesized via selenium-catalyzed reductive carbonylation of substituted nitrobenzenes with aminopyrimidine derivatives as co-reagents and carbon monoxide as carbonyl reagent instead of phosgene in one-pot reaction.

Novel nickel(II) and cobalt(II) catalysts based on poly-salen type ligands for the dimerization of propylene

A series of poly-salen type Ni(II) and Co(II) complexes were prepared, and the catalytic behavior in the dimerization of propylene has been studied in combination with aluminum co-catalysts and phosphine ligands. The effects of various reaction factors, such as the type of phosphine ligand and the P/Ni ratio, the type of aluminum co-catalyst and its quantity, particularly the nature of the nickel and cobalt complexes, were also examined. The results indicated that the productivity of the catalytic system was strongly dependent on the steric character of poly-salen ligand in the Ni(H) and Co(II) complexes. It was also found that reaction temperature deeply affected the performance of the catalytic system in the presence of phosphine ligand and alkyl aluminum promoter, and higher regioselectivities to 2,3-dimethylbutenes (2,3DMB) in the dimers were observed with incorporation of bulky and basic PCy3 into the nickel and cobalt catalysts. An extremely high activity in the propylene dimerization (TOF up to 221,000 h(-1)) was obtained with the 2b system under suitable conditions, which was much higher than that obtained with the corresponding monomeric salen system. However, it seemed difficult to realize recycling of the catalysts owing to the restrict dependence of catalytic activity with its solubility, at least under the adopted conditions