共查询到20条相似文献,搜索用时 140 毫秒
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提出了合成2,6-二氯嘌呤核苷和2-氯腺苷的新方法。 以商品化的2,6-二氯嘌呤和四乙酰核糖为原料,在5%(摩尔分数)三氟甲磺酸催化下,得到缩合物2',3',5'-三-O-乙酰基-2,6-二氯嘌呤核苷。 缩合物在浓H2SO4催化下,以89%的收率得到2,6-二氯嘌呤核苷;在NH3/CH3OH体系中氨解和脱除乙酰基,以92%的收率得到2-氯腺苷。 反应规模可以扩大到100 g,收率未降低。 该方法原料价格低廉,避免使用重金属催化剂,操作简便,中间体及产物可以通过结晶的方法纯化得到,显示出潜在的应用价值。 相似文献
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氯法拉滨是临床上唯一可以特异性地治疗儿童白血病的药物,2004年被美国食品和药物管理局批准上市.由于现有合成方法存在路线长、收率低和α/β异构体难以分离等问题,限制了该药物的广泛使用和进一步研究.以廉价且商品化的2-氯腺苷为原料,通过乙酸酐保护糖环上的3个羟基,在水合肼和乙酸作用下,选择性地脱除2'位的乙酰基.然后,以商品化的氟代试剂二乙胺基三氟化硫(DAST)进行2'位羟基的氟代反应,再使用NH3/MeOH饱和溶液脱除乙酰基可得氯法拉宾.这4步反应的总收率为49%,且得到的产品全部为β构型.同时,还发现2位取代基的位阻越大,越有利于选择性脱除2'位的乙酰基.本方法可以在克级规模上进行生产,收率无下降,同时中间体及产物的纯化不需要通过柱层析分离,显示出良好的应用前景?. 相似文献
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Kiyoshi Kikukawa Takatoshi Totoki Fumio Wada Tsutomu Matsuda 《Journal of organometallic chemistry》1984,270(3):283-287
Arenediazonium tetrafluoroborates (ArN2BF4 where Ar = X-C6H4; X = H, 2-Me, 3-Me, 4-Me, 4-MeO, 4-MeCO, 4-EtOCO, 2-Ph, 2-Cl, 3-Cl, 4-Cl, 4-Br, 4-I, 3-NO2 and 4-NO2) were easily converted to aromatic aldehydes (ArCHO) in good yields through the palladium-catalyzed reaction with CO and Et3SiH or polymethylhydrosiloxane (PMHS) at room temperature. 相似文献
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报道了配合物Ln(X-P)3·3H2O[其中X=H,2-Cl,4-Br,3-OH,3-NO2,2-OCH3,2-CH3,2,4-二氯,P=2-(COO)C6H4CONHC6H5-nXn,n=1,2;Ln=Pr(Ⅲ),Nd(Ⅲ)]的制备,并用元素分析、红外光谱、电子反射光谱、热重分析进行了表征。结果表明,配位是通过羧酸羟基氧原子和酰胺羰基氧原子进行的,含3分子配位水。通过电子反射光谱数据,对Slater-Condon参量(Fk)、Lande参量(ξ4f)、Nephelauxit比率(β),平均共价参数(δ)、平均成键参数(b1/2)、F4/F2、F6/F2比值进行了计算,对配合物的共价成键情况进行了讨论。 相似文献
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Kiyoshi Kikukawa Kazutoshi Ikenaga Kiyoshi Kono Koji Toritani Fumio Wada Tsutomu Matsuda 《Journal of organometallic chemistry》1984,270(3):277-282
Arenediazonium tetrafluoroborates (ArN2BF4 where Ar=Ph, 4-MeC6H4, 4-BrC6H4, 4-IC6H4 and 4-NO2C6H4) reacted easily with CH2=CHSiMe3 at 25 δC to give ArCH=CH2, (E-ArCH=CHSiMe3 and Ar(Me3Si)C=CH2 in excellent yields under palladium(O) catalysis. (E)-ArCH=CHSiMe3 compounds were obtained predominantly and isolated in good yields by using an excess of CH2=CHSiMe3 over ArN2BF4. Protodesilylation of the reaction mixture afforded styrene derivatives. 相似文献
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One series of 4-n-octyl-N-(4-X-benzylidene)anilines and two series of polar orthopalladated complexes derived from these of type Pd2(μ-Y)2 p-X-C6H3-CH = N-C6H4-C8H172; X: -H, -F, -Cl, -Br, -NO2, -CN, -CH3, -OCH3, -CF3, -COOCH3, -OCOCH3 and -OCOQH5; Y: -OAc and -Cl; have been synthesized and their mesogenic properties studied. In the polar Schiff bases used as organic ligands, the polar end group determines both the presence of the mesophase and the type of mesophase exhibited. In the complexes, however, it is the central structure of the molecule that practically always determines mesogenic behaviour. No acetato-bridged complex is mesogenic. All the chloro-bridged complexes, however, show mesogenic behaviour. All these compounds show smectic A mesophases with the exception of the CN compound, which only exhibits a nematic mesophase. 相似文献
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A facile preparation of nitrogen-doped β-TiO2(N-doped β-TiO2) nanobelts and their visible-light photocatalytic activity were reported. The preparation of N-doped β-TiO2 nanobelts consisted of cation-exchange between layered sodium titanate nanobelts and NH4+ in aqueous solution at room temperature and subsequent calcination in air. Such a calcination treatment is beneficial to the formation of monoclinic N-doped β-TiO2 nanobelts. Various measurement results indicate that not only were the nitrogen atoms doped into the lattice of β-TiO2 nanobelts resulting in a strong visible-light absorption, but also a large number of defects were caused by them in the lattice, increasing the stability of β-TiO2. The photocatalysis enhancement of N-doped β-TiO2 nanobelts for the photodegradation of Rhodamine B was demonstrated. 相似文献
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The substitution reactions of XC6H4COCl [X=2-, 3-, or 4-CH3; 2-, 3-, or 4-CH3O; 2-, or 4-I; or 2-, 3-, or 4-NO2] and YC6H4COONa [Y=2-, 3-, or 4-CH3; 2-, 3-, or 4-CH3O; 2-I; 4-NO2; or H] in a two-phase H2O/CH2Cl2 medium using pyridine-1-oxide (PNO) as an inverse phase transfer catalyst were investigated. In general, the kinetics of the reaction follows a pseudo-first-order rate law, with the observed rate constant being a linear function of the concentration of PNO in the water phase. In contrast to other analogous reactions, the hydrolysis reaction of 2-, 3-, or 4-NO2C6H4COCl in H2O/CH2Cl2 medium is catalyzed considerably by PNO and reaches an equilibrium. In the PNO-catalyzed reaction of XC6H4COCl and XC6H4COONa in H2O/CH2Cl2 medium, the order of reactivities of XC6H4COCl toward reaction with PNO in CH2Cl2 is 2-IC6H4COCl>4-IC6H4COCl>(C6H5COCl,3-CH3OC6H4COCl)>3-CH3C6H4COCl>(2-CH3C6H4COCl,4-CH3C6H4COCl)>4-CH3OC6H4COCl>2-CH3OC6H4COCl. Combined with the results of other analogous reactions, good Hammett correlations with positive reaction constant were obtained for the meta- and para-substituents, which supports that the XC6H4COCl–PNO reaction in CH2Cl2 is a nucleophilic substitution reaction. 相似文献
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氯合间取代四苯基卟啉铁与咪唑类配体配位反应的热力学研究 总被引:3,自引:0,他引:3
用紫外可见光谱法,在DMSO中测量了氯合间取代四苯基铁卟啉与多种咪唑类配体反应的平衡常数,研究了卟啉环上取代基、反应温度以及配体等因素对反应平衡常数的影响。利用温度系数法测定了反应体系的热力学函数ΔrHm和ΔrSm。 相似文献
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用丁烷代替苯为原料生产马来酸酐 ,是低碳烷烃选择氧化成功实现工业化的极少数例子之一 [1] ,其中 VPO复氧化物是唯一能高活性且高选择性地催化这一过程的催化剂 .因而 ,这一领域的研究备受关注 [2 ,3] .以 VPO铵盐单晶结构的研究为例 ,迄今已对α- NH4 V ( HPO4 ) [4 ] ,β- NH4 V ( HPO4 ) [5] ,NH4 VOPO4 [6 ] ,NH4 VOPO4 · H2 O[7] 和 α- NH4 VO2 HPO4 [8] 等进行了结构研究 .作为催化剂活性物质( VO) 2 P2 O7的前驱体 ,β- NH4 ( VO2 ) ( HPO4 )也曾被 Pulvin等 [9,10 ] 由粉末衍射数据推测分子组成为NH4 ( VO… 相似文献
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为了探究催化剂的结构和催化活性的关系,采用水热法制备了四种不同晶体结构的MnO2纳米催化剂(α-MnO2、β-MnO2、γ-MnO2和δ-MnO2),并考察了其低温NH3-SCR活性。结果表明,不同晶体结构催化剂的活性不同,依次为γ-MnO2 > α-MnO2 > β-MnO2 > δ-MnO2,γ-MnO2表现出最高的催化活性,NOx转化率在150-260℃超过90%。随后,通过X射线衍射(XRD)、扫描电子显微镜(SEM)、N2吸附-脱附、热重(TG)、红外光谱(FT-IR)、程序升温还原(H2-TPR)及吡啶吸附红外光谱(Py-FTIR)等表征手段对催化剂的结构和性质进行分析。结果表明,α-MnO2和β-MnO2为纳米棒,γ-MnO2和δ-MnO2为纳米针,催化剂的比表面积并不是影响低温NH3-SCR活性的主导因素。γ-MnO2具有适宜的孔道结构、较强的氧化还原能力、丰富的化学氧含量和Lewis酸酸性位点,是其具有最高低温NH3-SCR活性的原因。 相似文献
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G. Bator Th. Zeegers-Huyskens R. Jakubas J. Zaleski 《Journal of Molecular Structure》2001,570(1-3):61-74
Differential scanning calorimetry (DSC), dilatometric and dielectric measurements have been used to study the phase transitions in [C(NH2)3]3BiBr6. The [C(NH2)3]3BiBr6 crystal undergoes four phase transitions: at 419, 429, 475 and 495 K (on heating). The high-temperature phase transition is clearly of first-order type and its high entropy effect allows classifying it as of the order–disorder type. X-ray diffraction studies showed that [C(NH2)3]3BiBr6 crystallises in monoclinic, centrosymmetric space group, C2/c. The anionic sublattice is composed of isolated BiBr63− octahedra. The infrared between 100 and 350 K and Raman spectra at room temperature in the frequency range related to the internal vibrations of guanidinium cations were studied for [C(NH2)3]3BiBr6, [C(NH2)3]3Bi2Br9, [C(NH2)3]3BiCl6xCl2 and C(NH2)3Cl to analyse the dynamical state of cations. At room temperature, the cations in the studied guanidinium halogenobismuthates(III) are almost rigid, so the mechanism of high-temperature phase transitions is probably connected with the release of rotation of the cations. 相似文献