负载型钯催化剂硫中毒机理—模型催化剂的评价及表征

以H_2S为毒物,H_2-O_2反应为模型反应,用浸渍法制备了一系列Pd/Al_2O_3催化剂,用交替-脉冲微反应色谱技术对催化剂活性、耐硫性进行评价,用XPS、红外分析技术对不同反应阶段的催化剂进行了表征。结果表明:在一定条件下,虽然催化剂上有S_2~(2-)、S~(2-)和SO_4~(2-)物种存在,其活性也基本相同,但耐硫性差别较大。当催化剂上有S_2~(2-)存在时,其耐硫性较差,含有S~(2-)的催化剂次之,含有SO_4~(2-)的催化剂的耐毒性较好。SO_4~(2-)对催化剂的主要影响是降低了催化剂的活性,而对抗硫性影响不大。由此可以认为,H_2-O_2反应中负载型钯催化剂硫中毒时,以S_2~(2-)毒性最大,其次是S~(2-),在一定范围内SO_4~(2-)的毒性较小。     

Fe-FeCl3催化合成1,1,1,3,3-五氯丁烷的动力学研究

以Fe-FeCl3为催化剂、三苯基膦为助催化剂,对四氯化碳与2-氯丙烯调聚合成1,1,1,3,3-五氯丁烷进行了反应动力学研究.考察了催化剂用量、反应时间和反应温度对反应的影响,结果表明在n(CCl4):n(2-氯丙烯)=1.89:1.00,363～393 K下反应为一级反应,表观活化能为78.9 KJ/mol,对2-...     

钴的羟胺酸类配合物催化对-二甲苯氧化反应研究

合成并表征了 3种羟胺酸类钴配合物 Co(OTPHA) 2 、Co(OTBHA) 2 和 Co(OTOHA) 2 ,并对比评价了它们催化对 -二甲苯均相液相氧化合成对 -甲基苯甲酸的活性和选择性 .考察了以纯氧为氧源 ,常压下反应温度、催化剂浓度、反应时间以及水对反应转化率和选择性的影响 .实验结果表明 ,不同分子结构的配体 ,可以通过其空间效应和电子效应对催化活性产生直接的影响 ,3种催化剂的活性顺序为 :Co(OTPHA) 2 >Co(OTBHA ) 2 >Co(OTOHA ) 2 .当反应温度为 110℃、催化剂浓度 1.0× 10 - 3mol/ L、反应 6 h时 ,催化剂 Co(OTPHA) 2 的对 -二甲苯转化率可达 33.9%、选择性为 86 .2 % .若提高反应温度和加大催化剂浓度 ,则会降低催化剂的活性 .反应中生成的水对氧化反应有抑制作用 ,应及时将反应中生成的水从体系中分出     

环保增塑剂柠檬酸三(2-乙基)己酯的合成

以柠檬酸和2-乙基己醇为原料,用结晶硫酸高铈为催化剂合成环保增塑剂柠檬酸三(2-乙基)己酯,考察了反应温度、催化剂用量、醇酸摩尔比、反应时间等因素对反应结果的影响,对合成的产品进行了红外光谱分析。实验结果表明,硫酸高铈催化合成柠檬酸三(2-乙基)己酯的最佳反应条件为n(2-乙基已醇)∶n(柠檬酸)=3.60∶1,催化剂用量为柠檬酸质量的1.5%,反应时间为90 m in,反应温度为150℃~160℃,在最佳反应条件下,柠檬酸三(2-乙基)己酯收率在98%以上。     

手性噻唑烷-铑(I)配合物催化的苯乙酮不对称硅氢化反应

由L-半胱氨酸甲酯与α-吡啶甲醛缩合制备了2-(α-吡啶基)-4-羧甲基-1, 3-噻唑烷手性配体。用该手性配体与[Rh(COD)]2反应原位生成的Rh(I)配合物为催化剂进行了苯乙酮的不对称硅氢化反应。反应的化学产率达91%, 光学产率达82.1%e.e.。考察了各种反应条件对催化剂性能的影响。     

手性噻唑烷-铑(I)配合物催化的苯乙酮不对称硅氢化反应

由L-半胱氨酸甲酯与α-吡啶甲醛缩合制备了2-(α-吡啶基)-4-羧甲基-1, 3-噻唑烷手性配体。用该手性配体与[Rh(COD)]2反应原位生成的Rh(I)配合物为催化剂进行了苯乙酮的不对称硅氢化反应。反应的化学产率达91%, 光学产率达82.1%e.e.。考察了各种反应条件对催化剂性能的影响。     

对硝基苯磺酰基乙酸酯与芳香醛的缩合反应

对硝基苯磺酰基乙酸酯与芳香醛在六氢吡啶醋酸盐催化下发生缩合反应生成α,β-不饱和砜,研究了催化剂对反应影响,发现DPA(3-Dimethylaminophenylpropylamine)是最有效的催化剂,可以替代六氢吡啶。在NaCl/DMSO/H2O体系中,缩合产物2-(对硝基苯磺酰基)-3-苯丙烯酸乙酯在185℃反应,得到脱羧物E-2-(对硝基)苯磺酰基苯乙烯。用1HNMR确证了缩合产物构型为E。     

5(6)-氨基-1-(4-氨基苯基)-1,3,3-三甲基茚满合成及工艺优化

以5(6)-硝基-1-(4-硝基苯基)-1,3,3-三甲基茚满为原料,Pd/C为催化剂,用氢气还原合成5(6)-氨基-1-(4-氨基苯基)-1,3,3-三甲基茚满。红外、核磁表征了产物结构;考察了反应温度、反应时间、充入氢气压力及催化剂用量四个因素,设计正交试验对还原工艺条件进行优化分析。结果表明,对粗产率的影响显著程度依次为充入H2压力、反应时间、反应温度和催化剂用量,获得了优化工艺条件,即反应温度70℃、反应时间为2 h、充入H2压力为1.5 MPa,催化剂用量为5(6)-硝基-1-(4-硝基苯基)-1,3,3-三甲基茚满的10%。     

碘掺杂聚苯胺催化合成环己酮1,2-丙二醇缩酮

合成了聚苯胺-碘(PAn-I2)催化剂,并对其结构进行了表征。并通过环己酮与1,2-丙二醇合成环己酮1,2-丙二醇缩酮,探讨了PAn-I2对缩酮反应的催化活性。实验结果表明,PAn-I2是缩酮反应的良好催化剂,在环己酮100 mmol,n(环己酮)∶n(1,2-丙二醇)=1∶1.5,催化剂用量为反应物总质量的3%,环己烷12 mL,反应时间2 h的优化条件下,环己酮1,2-丙二醇缩酮的收率可达92.1%。     

B108中温变换催化剂宏观动力学的研究

常压下以内循环无梯度反应器研究了B108铁基中温变换催化剂上水煤气变换反应宏观动力学。测定了反应速率,并用马夸特非线性参数估值法获得了幂函数宏观动力学模型r_s=37.67exp(-43982/RT)y_(CO)~(0.7552)y_(H_2O)~(-0.0367)Y_(CO_2)~(-0.4874)y_(H_2)(1-β)根据方差分析和残差分析,证实模型是高度显著的。由实验数据计算出相应反应条件下的效率因子。内扩散对原粒度B108催化剂上的反应具有严重影响。模型用于工业变换炉催化剂的用量核算,模型值与实际值符合良好。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.