The redox behaviour of cyclic tetraaminoethenes derived from 2,2′-biimidazole

Syntheses and redox chemistry of the nearly unknown 4,4′,5,5′-tetraamino derivatives of 2,2′-biimidazole are studied. These cyclic versions of electron-rich ethenes are only stable under strictly anaerobic conditions. In the presence of oxygen, a fast oxidation reaction occurs to form stable, deeply coloured tetraazafulvalenes. Leuco-forms, however, can be stabilized towards air by acylation reactions. This accounts for the hexa-Boc derivative 6. Based on these findings, we present the first synthesis of tetraazafulvalenes, which possess four peripheric secondary amine functions.     

Water／Oil Biphasic Hydroformylation of Higher Olefins over a TPPTS-Rh／SiO2 Catalyst

A novel TPPTS-Rh/SiO2 catalyst, prepared by directly modifying a heterogeneous high-surface-area Rh/SiO2 catalyst with water-soluble TPPTS ligands, could decrease the resistance of masstransfer in water/oil biphasic media for the hydroformylation of higher olefins. The catalytic performancefor hydroformylation on this biphasic TPPTS-Rh/SiO2 catalyst system was higher than those of thetraditional biphasic HRhCO(TPPTS)3 systems, owing to the chemical bonds between the highly dispersedRh metal particles and the TPPTS ligands. The catalyst system is applicable for hydroformylation ofhigher olefins such as 1-dodecene.     

Captodative olefins: methyl 2-aryloxy-3-dimethyl-aminopropenoates and their application in a new synthesis of benzofurans

The β-substituted captodative olefins methyl 2-aryloxy-3-dimethylaminopropenoates 4a-h were synthesized, via aminomethylenation of the corresponding 2-phenoxyacetic esters 9a-h. Lewis acid promoted intramolecular cyclization of alkenes 4 led to benzofurans 7a-h, in an efficient synthetic approach to the benzofuran frame.     

Polystyrene-supported Benzyl Selenide: An Efficient Reagent for Highly Stereocontrolled Synthesis of Substituted Olefins

Solid-phase methodology has been rapidly and extensively applied to the preparation of small organic molecules recently1. It might be argued that selenoxide syn-elimination provided the principal impetus for the development of organoselenium chemistry. In addition, the required selenoxides are readily available from the oxidation of the corresponding selenides, which in turn can be prepared by the reaction of selenium-stabilized carbanions with various electrophilic substrates2. However, or…     

The use of bis(diphenylphosphino)amines with N-aryl functionalities in selective ethylene tri- and tetramerisation

A systematic study was conducted on the Cr catalysed tri- and tetramerisation of ethylene using bis(diphenylphosphino)amine ligands with N-aryl functionality. This study revealed that the oligomerisation reaction product selectivity is primarily dependent on the structure and size of the N-aryl groups.

Addition of sufficient steric bulk to the N-phenyl group via ortho-alkyl substitution increased the combined 1-hexene and 1-octene selectivity (overall alpha selectivity) to above 82% at an overall 1-octene selectivity of 56%. The introduction of a single carbon spacer between the N-atom and the aryl-moiety, as well as the addition of branching on this carbon, resulted in further selectivity improvements, achieving an overall 1-octene selectivity of 64% and an overall alpha selectivity of 84%. This was obtained at catalyst productivities in excess of 1,000,000 g/g Cr/h.     

磷化氢与环烯烃反应的原位^3^1P NMR研究

本文应用加压原位核磁共振波谱技术, 在反应温度50-70℃、反应压力1.0-2.0MPa, 氘代苯为溶剂, 偶氮二异丁腈为引发剂的条件下, 考察了磷化氢与环烯烃1, 5-环辛二烯、双环戊二烯、1, 3-环己二烯、1, 4-环己二烯及1, 5, 9-环十二三烯的反应。实验结果表明, 磷化氢与1, 5-环辛二烯反应主要生成双环膦杂环壬烷; 与其它环烯烃均不生成膦杂环化合物, 仅为一取代伯膦或二取代仲膦产物。磷化氢与环烯烃反应仍为串行机理。     

Polymer bound glutamic acid salicylaldehyde Schiff‐base complex ­catalyst for oxidation of olefins with ­dioxygen

The polymer bound Schiff‐base ligand (PS‐SalGlu) has been prepared from polystyrene bound salicylaldehyde and glutamic acid, and its complex (PS‐SalGlu‐Co) has also been synthesized. The polymer ligand and its complex were characterized by infrared spectroscopy, small area X‐ray photoelectron spectroscopy, and inductively coupled plasma‐atomic emission spectro (ICP‐AFS). In the presence of the complex, cyclohexene can be effectively oxidized by molecular oxygen without reductant. The long‐chain linear aliphatic olefins, such as 1‐octene, 1‐decene, 1‐dodecene and 1‐tetradecene, can be directly oxidized by molecular oxygen catalyzed by PS‐SalGlu‐Co, which affords the 1,2‐epoxy alkane. Copyright © 2001 John Wiley & Sons, Ltd.     

Mechanism of Cp<Subscript>2</Subscript>ZrCl<Subscript>2</Subscript>-catalyzed olefin hydroalumination by alkylalanes

The composition of intermediates of the Cp₂ZrCl₂-catalyzed hydroalumination of α-olefins by isobutylalanes (HAlBuⁱ ₂, AlBuⁱ ₃, ClAlBuⁱ ₂) was studied by dynamic ¹H and ¹³C NMR pectroscopy. The reaction of Cp₂ZrCl₂ with isobutylalanes affords the complex (Cp₂ZrHCl·HAlBuⁱ ₂)₂ responsible for α-olefin hydroalumination.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 311–322, February, 2005.     

Fe—Silicalite—2催化剂表面CO2加氢反应性能的研究

研究了Ｆｅ／Ｓｉｌｉｃａｌｉｔｅ－２催化剂ＣＯ２加氢低碳烯烃反应性能，利用ＣＯ２－ＴＰＤ，ＣＯ２／Ｈ２－ＴＰＳＲ和ＣＯ／Ｈ２－ＴＰＳＲ表征手段，考察了铁含量及ＭｎＯ助剂对Ｆｅ／Ｓｉｌｉｃａｌｉｔｅ－２催化剂ＣＯ２吸附脱附及加氢反应性能的影响，表明随铁含量增加可提高催化剂对ＣＯ２的吸附能力，有利于提高ＣＯ２加氢反应的转化率。     

C4/C5烃催化裂解制低碳烯烃的研究进展

从催化剂类型、裂解工艺、催化裂解的影响因素和裂解机理4个方面对国内外C4／C5烃催化裂解制低碳烯烃的研究进行了综述。催化裂解制低碳烯烃催化剂主要采用ZSM-5分子筛系列催化剂，在此基础上发展了酸改性或水热改性高硅ZSM系列分子筛及介孔MCM41分子筛。总结了国内外C4／C5烃的裂解工艺，认为影响催化裂解的主要因素是裂解原料、催化剂类型及工艺条件。目前，裂解机理主要是自由基与碳正离子机理相结合的机理。并简述了本课题组目前有关C4烷烃催化裂解的主要研究进展。