三溴甲基芳烃合成新方法的研究

报道了一种以三氯甲基芳烃与三溴化硼反应制备系列三溴甲基芳烃的新方法. 该方法反应条件温和, 收率高, 选择性好. 同时, 对影响该反应的因素进行了研究, 发现当芳环上连有强吸电子基团时, 不利于反应的进行, 而连有推电子基团时, 则有利于反应进行; 当取代基处于邻位时, 则明显阻碍反应的进行. 采用这种方法已合成了十多个三溴甲基芳烃, 其中1个是未见文献报道的新化合物.     

有机化合物的氧化溴化研究进展

综述了几类在氧化剂存在下的羰基α位、芳环、烯烃双键、烷基苯苄位及烷烃上的氧化溴化反应。氧化溴化体系主要有Br-/H2O2和Br-/BrO3-体系。总结了不同反应条件对反应收率的影响,并展望了该领域的研究前景。     

新型高选择性芳环溴化剂

苄基三甲基三溴化铵是新型高选择性的芳环溴化剂。在ＣＨ２Ｃｌ２－ＣＨ３ＯＨ或ＣＨ３ＣＯＯＯＨ－ＺｎＣｌ２中，它与酚，芳胺，酰胺，芳醚，芳烃及芳杂环化合物等反应，选择性得到对应的单，双或三溴化产物。     

nbs与取代苯的亲电反应及其应用

选取含不同取代基的甲苯在不同条件下与NBS反应,考察了溶剂极性、取代基的电子效应和温度等因素对反应结果的影响,结果表明,取代反应的区域选择性强烈地依赖于反应溶剂和取代基的电子效应及其数量。随反应溶剂极性的增强,芳环上亲电取代产物的比例增加;随芳环上取代基的推电子能力的增大,亲电取代反应的优势愈加明显;相反,则有利于α-位上的游离基取代。在此基础上,研究了溴化Q0的合成方法,形成了一条新的、简便的溴化Q0的合成路线,收率达86％以上。     

甲基芳烃的侧链溴化新方法研究

溴苄类化合物在医药、农药和染料等领域有广泛的应用, 在以往的报道中由甲基芳烃制备溴苄类化合物的方法都是采用自由基的历程进行的. 报道了一种以甲基芳烃与三溴化硼直接反应采用非自由基的历程制备系列溴甲基芳烃的新方法. 该方法反应条件温和、收率高、选择性好. 在考察电子效应和位阻效应时发现: 该方法对不同取代基的底物适应范围广, 带推电子取代基对反应有利; 取代基位阻有一定影响但是没有吸电子基团显著, 吸电子基团降低产率. 同时, 在研究溶剂、温度、三溴化硼用量和时间对反应的影响时找到了最佳反应条件.     

载溴树脂作为活泼芳香族化合物的溴化剂

用载溴树脂作为间甲基茴香醚、间甲酚等活泼芳香化合物的溴化剂，得到一溴代产物，产率为75～85%。该试剂反应条件温和，选择性好，是一种有效的活泼芳环的溴化剂。离子交换树脂可回收使用。     

室温下二氧化氮催化带有给电子取代基的苯和萘的氧化溴化

在室温下,以8.2%的二氧化氮为催化剂,反应管中残留的空气为氧化剂,分子溴为溴化试剂,研究了带有给电子取代基的苯和萘的氧化溴化.使用的低沸点非金属催化剂易于从产物中去除,很少玷污最终产品;但反应后有少量的苯环硝化副产物生成,这会造成催化剂二氧化氮的损耗.反应具有较高的原子经济性,大部分溴原子被转化到产物中.反应产物具有可控性:可通过改变溴源的用量,分别得到单溴化和二溴化产物.初步的机理分析结论为:反应可能经历分子溴和芳环的反应,生成溴代芳烃和溴化氢;然后在氧化氮类物种催化下,生成的溴化氢被氧气氧化为具有反应活性的溴.     

7-O-取代-8-甲基香豆素和4H-色烯-4-酮化合物与NBS/CCl_4试剂的溴化反应

7-O-取代-8-甲基香豆素和4-H-色烯-4-酮化合物是合成Seco-DCK和Seco-DCP类似物的重要中间体.报道了在NBS/CCl4条件下,这两类化合物8-位甲基溴代反应的情况.通过实验发现,这两类化合物8-位甲基溴代反应较一般芳环苄位的溴代更为复杂,存在多个反应位点.影响8-位甲基溴代选择性和收率的主要因素有三:邻位基团空间位阻大小、自由基引发催化剂的使用与否以及邻位基团的电性因素.通过控制反应条件,可以中等收率得到8-位甲基溴代化合物.     

无配体铜催化芳溴和K_4[Fe(CN)_6]的氰化

铜催化芳溴氰化反应通常在惰性气体保护下进行, 而且配体和碱的使用也是必要的. 本文发现无配体的Cu(OAc)_2·H_2O能够有效地催化芳溴的氰化;并且反应无需使用碱, 无需惰性气体保护;为芳腈的合成提供一种经济有效的方法. 此方法可应用到多种芳溴的腈化, 在16种芳溴底物反应的例子中, 得到了56%-94%的产率.     

无配体铜催化芳溴和Ｋ４［Ｆｅ（ＣＮ）６］的氰化

铜催化芳溴氰化反应通常在惰性气体保护下进行,而且配体和碱的使用也是必要的．本文发现无配体的Ｃｕ（ＯＡｃ）２·Ｈ２Ｏ能够有效地催化芳溴的氰化;并且反应无需使用碱,无需惰性气体保护;为芳腈的合成提供一种经济有效的方法．此方法可应用到多种芳溴的腈化,在１６种芳溴底物反应的例子中,得到了５６％９４％的产率．     

Bromination of deactivated aromatics: a simple and efficient method

Highly deactivated aromatic compounds were smoothly monobrominated by treatment with N-bromosuccinimide (NBS) in concentrated H2SO4 medium affording the corresponding bromo derivatives in good yields. Mild reaction conditions and simple workup provides a practical and commercially viable route for the synthesis of bromo compounds of deactivated aromatics.     

Friedel-Crafts and modified Vorbrüggen ribosylation. A short synthesis of aryl and heteroaryl-C-nucleosides

A direct coupling of aryl donor and tetra-O-acetylribose in the presence of Lewis acid led to β-C-nucleosides in good yields. In contrast, for deactivated electron-poor aromatics, a modified Vorbrüggen ribosylation reaction was investigated and successfully applied in the case of 2-trimethylsilyl-thiazole.     

Enhanced Stability of Mo-Promoted Zn/HZSM-5 Catalyst for Methanol to Aromatics

A Mo-promoted Zn/HZSM-5 catalyst was prepared by isometric impregnation method (IM). The physicochemical properties of catalysts were characterized by X-ray diffraction, registration of N₂ adsorption-desorption isotherms, transmission electron microscopy, NH₃ temperature-programmed desorption and IR spectroscopic study of pyridine adsorption. The results show that by doping zeolite with Mo species it is possible to tune the microstructures, acidity and crystallinity of the catalyst. Additionally, it was found that the 1%Mo(IM)–5%Zn(IE)/HZSM-5 catalyst had a high catalytic activity and stability for methanol to aromatics (MTA) reaction. The yield of aromatics reached 77.3% at 450°C and TOS = 3 h. When the TOS = 98 h, the yield of total aromatics remains at a 60.4% level. The lifetime of catalysts was influenced by the synergetic effect of Brønsted and Lewis acid sites, so the modification with Mo may bring an opportunity to prolong the lifetime of Zn/HZSM-5 catalyst in the MTA reaction. The metal components are sintered and lost in continuous reaction-regeneration cycles. Accordingly, the activity of deactivated catalyst cannot be completely restored to the initial level.     

MCM-41和HZSM-5协同催化对油菜秸秆热解的影响

以油菜秸秆为原料,采用两种方案分层布置催化剂(HZSM-5/MCM-41和MCM-41/HZSM-5),并与MCM-41和HZSM-5单独催化进行对比,从生物油品质和催化剂耐久性两个角度探究协同催化作用机理;对精制生物油有机相进行理化特性分析,采用FT-IR和GC-MS进行成分分析,对催化剂进行耐久性分析。结果表明,与单独催化相比,协同催化所得精制生物油液相产率略有降低,气相产率升高,精制生物油有机相理化特性进一步提高,其中,MCM-41/HZSM-5协同催化所得精制生物油有机相热值较高,为34.31 MJ/kg;精制生物油有机相中含有多种芳香族类物质和少量的羰基类物质,协同催化较单独催化能产生较多的烃类物质及较少的含氧芳香族类物质,其中,MCM-41/HZSM-5协同催化所得精制生物油有机相中烃类物质含量较高,且以单环芳香烃为主;HZSM-5分子筛在300-800℃有两个失重峰,MCM-41分子筛在300-800℃仅有一个失重峰,表明MCM-41催化剂上沉积的焦炭成分单一,较易去除,且协同催化后分子筛表面沉积的焦炭总含量较少。     

Chemistry of superacids

Superelectrophilic nitration of deactivated aromatics with NO₂Cl−3MX _n complexes in aprotic nonpolar solvents such as CH₂Cl₂ makes it possible to obtain the corresponding nitro derivatives in good to almost quantitative yields under mild conditions. For part 34, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 953–956, May, 1998.     

离子液体催化脱除芳烃中微量烯烃的研究

以室温离子液体为催化剂,对芳烃中的微量烯烃杂质进行深度脱除。考察了离子液体种类、用量、温度等不同因素对烯烃脱除效果的影响。结果表明,[bmim]Br-AlCl₃离子液体显示了优良的催化性能,在离子液体的质量分数为5%、室温、反应10min下,溴指数从原料的773.5下降到10以下,芳烃中微量烯烃脱除率达到99%以上,离子液体可重复使用,并对反应机理进行了研究。     

Pd‐PEPPSI‐IPent‐SiO2: A Supported Catalyst for Challenging Negishi Coupling Reactions in Flow

A silica‐supported precatalyst, Pd‐PEPPSI‐IPent‐SiO₂, has been prepared and evaluated for its proficiency in the Negishi cross‐coupling of hindered and electronically deactivated coupling partners. The precatalyst Pd‐PEPPSI‐IPent loaded onto packed bed columns shows high catalytic activity for the room‐temperature coupling of deactivated/hindered biaryl partners. Also for the first time, the flowed Csp³–Csp² coupling of secondary alkylzinc reagents to (hetero)aromatics has been achieved with high selectivity with Pd‐PEPPSI‐IPent‐SiO₂. These couplings required residence times as short as 3 minutes to effect completion of these challenging transformations with excellent selectivity for the nonrearranged product.     

不同结构的芳烃对加氢裂化催化剂积炭的影响

在高压连续流动微型反应器上采用催速老化技术考察了不同结构的芳烃在加氢裂化催化剂上积炭行为，并用热分析、傅立叶变换红外和物理吸附仪等手段对积炭催化剂的积炭类型、酸强度分布和孔结构的变化进行了研究。结果发现：单环芳烃中，随着取代基的碳链长度、数目及不饱和度的增加，催化剂更容易积炭。稠环芳烃的环数越多，反应生成的总积炭和假石墨型积炭越多。积炭越多的催化剂，比表面积降低越多。积炭主要沉积在催化剂的小孔内或堵塞小孔孔口，有些积炭在催化剂表面形成机械孔。积炭后，催化剂上不同强度的酸数目均较新鲜催化剂降低，尤其是萘和菲，使强酸严重削弱。     

Perhalogenmethylmercapto-heterocyclen, (VII) [1] konkurrenzreaktionen elektronenarmer,substituierter aromaten um die halogenmethylmercapto- BZW. Chlorgruppe von Cl3-nFnCSCl in starken saeuren

Electron-deficient aromatics, such as 2,5-bis(trifluoromethylmercapto)thiophene ($\text{1a}$) or (trifluoromethylmercapto)benzene ($\text{8a}$), react with F₃CSCl in the presence of F₃CSO₃ as a catalyst to give mainly 3-chloro-2,5-bis(trifluoromethylmercapto)thiophen ($\text{3a}$) and 1-chloro-4- or 2-(trifluoromethylmercapto)benzene ($\text{10}$, respectively. This reaction competes with the one expected to result in 2,3,5-tris(trifluoromethylmercapto)thiophene ($\text{2a}$) and 1,4- and 1,2-bis(trifluoromethylmercapto)benzene ($\text{9}$,$\text{9′}$), respectively. Further reactions of deactivated aromatics with Cl_3-nF_nCSCl show that the chlorine substitution is in general catalysed by strong acids. Reaction mechanisms are proposed for both Substitutions. The Cl_3-nF_nCS group in aromatics exerts a -M-effect in the case of an attack of a positive ion, e.g. H^⊕, the well-known +M-effect in the case of reactions with positively polarized molecules, e.g. CF₃S^β+Cl^β-.     

The aza-Morita-Baylis-Hillman reaction of electronically and sterically deactivated substrates

The aza-Morita-Baylis-Hillman (azaMBH) reaction has been studied for electronically and sterically deactivated Michael acceptors. It is found that electronically deactivated systems can be converted with electron-rich phosphanes and pyridines as catalysts equally well. For sterically deactivated systems clearly better catalytic turnover can be achieved with pyridine catalysts. This is in accordance with the calculated affinities of the catalysts towards different Michael-acceptors.