51233-74-0Relevant articles and documents
Understanding the mechanism of N coordination on framework Ti of Ti-BEA zeolite and its promoting effect on alkene epoxidation reaction
Liang, Xiaohang,Liu, Dan,Luo, Yibin,Peng, Xinxin,Shu, Xingtian,Xia, Changjiu
, (2021/07/31)
The function of ammonium salts on the epoxidation performance over Ti-BEA zeolite was investigated in detail. Experiments of alkene epoxidation, side reactions of epoxide and decomposition of H2O2 with or without ammonium salts were designed, and the UV-Vis spectroscopy was employed to analyze the structure of Ti-hydroperoxo species. It is revealed that the ammonia (or amines) dissociated from the ammonium salt would chelate with the linear Ti-η1(OOH) species and form a bridged Ti-η2(OOH)-R species, which is more stable, more weaker in epoxide adsorption and acidity as well. Therefore, side reactions and H2O2 decomposition would be suppressed, and both alkene conversion and epoxide selectivity would be promoted simultaneously. On the other hand, the excessive NH3?H2O (NH3/Ti>1) or NaOH bond with the Ti-η2(OOH)-R species and generate salt-like Ti-η2(OO)-M+ species, resulting in the deactivation of Ti active center. While for ammonium salts, e.g. NH4Cl, the limited dissociation degree along with the acidic environment help the Ti active center to maintain in highly active. In short, this work provides a practical Ti active center tuning method for Ti-BEA zeolite, as well as a thorough understanding of its Ti-hydroperoxo species.
Asymmetric synthesis of O-protected acyloins using enoate reductases: Stereochemical control through protecting group modification
Winkler, Christoph K.,Stueckler, Clemens,Mueller, Nicole J.,Pressnitz, Desiree,Faber, Kurt
experimental part, p. 6354 - 6358 (2011/02/24)
O-Protected cyclic acyloins were obtained in nonracemic form through asymmetric bioreduction of α,β-unsaturated alkoxy ketones by using 11 different enoate reductases from the "Old Yellow Enzyme" family. The stereochemical outcome of the biotransformation could be switched by variation of the O-protecting group or by the ring size of the substrate, which allows access to both stereoisomers in up to >97 % ee Whereas α-alkoxy enones were readily accepted as substrates, β-analogs were not converted. Overall, α-alkoxy enones represent a novel type of substrate for flavin-dependent ene-reductases. Copyright
Reaction-controlled phase-transfer catalytic oxidative cleavage of cyclopentene to glutaraldehyde over peroxy-niobic acid
Chen, Hao,Dai, Wei-Lin,Jiang, An-Ren,Deng, Jing-Fa
, p. 220 - 221 (2007/10/03)
The oxidative cleavage of cyclopentene to glutaraldehyde with aqueous H2O2 was performed over a peroxy-niobic acid catalyst with high yield (72%) and complete conversion of cyclopentene under mild reaction conditions. Peroxy-niobic acid has been shown as a "reaction-controlled phase-transfer" catalyst, which has the advantages of both homogeneous and heterogeneous catalysts.
Chiral synthesis via organoboranes. 45. Asymmetric hydroboration of 1-cyclopentenol derivatives using diisopinocampheylborane. Synthesis of optically active cyclopentane-1,2-diol derivatives of high optical purity
Brown, Herbert C.,Murali, Dhanabalan,Singaram, Bakthan
, p. 116 - 121 (2007/10/03)
The asymmetric hydroboration of 1-cyclopentenol derivatives, such as ethers, acetate, silyl ether and borinate, was investigated using diisopinocampheylborane, dIpc2BH. The product trialkylboranes were treated with excess of acetalde
A new process for preparing dialdehydes by catalytic oxidation of cyclic olefins with aqueous hydrogen peroxide
Deng,Xu,Chen,Jiang
, p. 3503 - 3514 (2007/10/02)
Dialdehydes were prepared by the reaction between cyclic olefins and aqueous hydrogen peroxide catalyzed by tungstic acid. Glutaraldehyde and adipaldehyde were synthesized by this method with good yield. Several different conditions were tested.
