Novel reaction of 1-aryl-2-bromodiazene 1-oxides with olefins. Synthesis of 1-aryl-2-(2-bromoalkyl)diazene 1-oxides

The addition of 1-aryl-2-bromodiazene 1-oxides to olefins yields 1-aryl-2-(2-bromoalkyl)diazene 1-oxides (4). A radical mechanism of the reaction has been suggested. Compounds4 decompose to give bromohydrazones of formaldehyde and aldehydes. The structural factors that affect the rate of this process are discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 917–923, May, 1995.The work was carried out in the Scientific Educational Center of the Institute of Organic Chemistry of the RAS with financial support of the Russian Foundation for Basic Research (Project No. 93-03-18461).     

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.     

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.     

CO加氢制备低碳烯烃Fe基、Co基催化剂研究进展

CO加氢制备低碳烯烃是非石油路线获得烯烃的重要反应,其反应路线有直接法和间接法。直接法制备低碳烯烃具有反应路线短、能源利用率高、经济高效等优势。综述了近年来Fe基催化剂、Co基催化剂在CO直接制备低碳烯烃中的研究进展。分析认为：费托合成过程产物选择性遵循Anderson-Schulz-Flory（ASF）分布规律,助剂和载体的使用一定程度提高Fe基、Co基催化剂的低碳烯烃选择性。     

ZSM-5催化丙烯芳构化反应构效关系及反应特性

甲醇两步制芳烃反应中低碳烯烃芳构化反应稳定性优异,为分析其内在机制,制备了不同硅铝比（n_SiO2/n_Al2O3）及Zn负载量的ZSM-5催化剂,以丙烯芳构化为模型反应,分析ZSM-5表面酸性对低碳烯烃芳构化反应性能的影响规律,并探究反应微观特性。发现当硅铝比由150降至75时,增加的酸密度促进了烯烃氢转移芳构化过程,使芳烃选择性由31.0%增至34.4%,但丙烯直接参与的氢转移过程也被强化,使丙烷产物选择性由28.2%增至36.0%。引入Zn助剂可将部分Brønsted酸转变为Zn-Lewis酸,强化烯烃脱氢芳构化过程,使芳烃选择性进一步显著增加到62.4%。丙烯芳构化过程中芳烃烷基化深度比甲醇芳构化过程低,提升总芳烃选择性的同时,也明显抑制了难溶性积碳的形成,使反应稳定性明显提升。由此得出,甲醇两步制芳烃过程中甲醇制低碳烯烃过程对甲醇的预先消耗,抑制了低碳烯烃芳构化反应芳烃产物的深度烷基化,是该反应表现出优异稳定性的重要原因。     

Effect of Phenyl CI Substituent Position on the Catalytic Performance for Olefin Epoxidation of Tetraphenylmetalloporphyrins

以苯乙烯、环己烯和反式二苯乙烯为烯烃底物,以双氧水、叔丁基过氧化氢和异丙苯过氧化氢为氧化剂,以苯环上对位和邻位氯取代的四苯基金属卟啉为仿生催化剂,对烯烃的催化环氧化反应进行了对比研究.讨论了不同氯取代位的四苯基金属卟啉对烯烃环氧化性能的影响.实验结果表明,在没有助催化剂存在下,邻位氯代的四（2,6-二氯苯基）铁（锰）卟啉对烯烃的环氧化具有优异的催化性能,烯烃底物的转化率和环氧选择性都比对位氯代的四苯基铁（锰）卟啉高,且反应条件温和.其中FeⅢ（TDCPP）Cl的催化性能最好,环氧化选择性最高,催化氧化苯乙烯时,环氧苯乙烷的选择性达到了90.4%.相同金属离子不同配体的金属卟啉传递氧原子的能力为TDCPP〉T（p-Cl）PP〉TPP.氧化剂的结构对环氧化物的选择性有较大影响.过氧键连有吸电子基团的异丙苯过氧化氢对环氧化物的选择性最高.根据实验结果,对金属卟啉催化环氧化机理进行了分析.     

A Rapid and Simple Method for Quantitative Aziridination from Aminobrominated Derivatives of Olefins under Solvent‐free and Mild Conditions

The urea‐catalyzed aziridination of 1,2‐vicinal haloamines derived from aminohalogenation of olefins has been developed. This rapid and simple method was carried out by simply grinding the solid mixture of the substrate, K₂CO₃ and catalytic amount of urea at room temperature in air. The reaction provides a protocol for quantitative preparation of aziridines in a large scope of aminohalogenated derivatives of olefins including α,β‐unsaturated ketones, α,β‐unsaturated esters and simple olefins. The possible mechanism involving an H‐bond promoting deprotonation has been suggested for this reaction.     

Rhodium-catalyzed asymmetric hydrogenation of olefins with PhthalaPhos, a new class of chiral supramolecular ligands

A library of 19 binol-derived chiral monophosphites that contain a phthalic acid diamide group (PhthalaPhos) has been designed and synthesized in four steps. These new ligands were screened in the rhodium-catalyzed enantioselective hydrogenation of prochiral dehydroamino esters and enamides. Several members of the library showed excellent enantioselectivity with methyl 2-acetamido acrylate (6 ligands gave >97% ee), methyl (Z)-2-acetamido cinnamate (6 ligands gave >94% ee), and N-(1-phenylvinyl)acetamide (9 ligands gave >95% ee), whilst only a few representatives afforded high enantioselectivities for challenging and industrially relevant substrates N-(3,4-dihydronaphthalen-1-yl)-acetamide (96% ee in one case) and methyl (E)-2-(acetamidomethyl)-3-phenylacrylate (99% ee in one case). In most cases, the new ligands were more active and more stereoselective than their structurally related monodentate phosphites (which are devoid of functional groups that are capable of hydrogen-bonding interactions). Control experiments and kinetic studies were carried out that allowed us to demonstrate that hydrogen-bonding interactions involving the diamide group of the PhthalaPhos ligands strongly contribute to their outstanding catalytic properties. Computational studies carried out on a rhodium precatalyst and on a conceivable intermediate in the hydrogenation catalytic cycle shed some light on the role played by hydrogen bonding, which is likely to act in a substrate-orientation effect.     

Single isomer trisubstituted olefins bearing alkyl groups

E-β-Chloro-α-iodo-α,β-unsaturated esters were converted to single isomer trisubstituted olefins bearing alkyl substituents by using and alkyl-Suzuki cross coupling. The process was highly selective, and the products in all cases were isolated as single isomers. Mechanistic investigations indicated that this process transfers a hydrogen from water to the α-position of the substrate, and then an alkyl group is introduced to the β-position of the intermediate template while replacing a chloride.