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21.
The first total synthesis of the natural product (−)-petrosiol D has been achieved in a linear fashion. Sharpless asymmetric epoxidation, base induced elimination reaction for the formation of chiral propargyl alcohol and Cadiot–Chodkiewicz coupling reaction are the key steps utilized for the synthesis. 相似文献
22.
Treatment of Pd(PPh3)4 with 5‐bromo‐pyrimidine [C4H3N2Br] in dichloromethane at ambient temperature cause the oxidative addition reaction to produce the palladium complex [Pd(PPh3)2(η1‐C4H3N2)(Br)], 1 , by substituting two triphenylphosphine ligands. In acetonitrile solution of 1 in refluxing temperature for 1 day, it do not undergo displacement of the triphenylphosphine ligand to form the dipalladium complex [Pd(PPh3)Br]2{μ,η2‐(η1‐C4H3N2)}2, or bromide ligand to form chelating pyrimidine complex [Pd(PPh3)2(η2‐C4H3N2)]Br. Complex 1 reacted with bidentate ligand, NH4S2CNC4H8, and tridentate ligand, KTp {Tp = tris(pyrazoyl‐1‐yl)borate}, to obtain the η2‐dithiocarbamate η1‐pyrimidine complex [Pd(PPh3)(η1‐C4H3N2)(η2‐S2CNC4H8)], 4 and η2‐Tp η1‐pyrimidine complex [Pd(PPh3)(η1‐C4H3N2)(η2‐Tp)], 5 , respectively. Complexes 4 and 5 are characterized by X‐ray diffraction analyses. 相似文献
23.
在pH4.0的介质中,Mo(Ⅵ)与新试剂4-(5-溴-2-噻唑偶氮)邻苯二酚(5-Br-TAPC)和二苯胍(DPG)反应形成稳定的三元离子缔合物,其组成比Mo(Ⅵ):5-Br-TAPC∶DPG为1∶3∶2。该三元缔合物氯仿萃取液的λmax为536nm,对比度为119nm,表观ε为6.33×104L·mol-1·cm-1。钼(Ⅵ)含量在0~0.80mg/L范围内遵从比耳定律,并探讨了离子缔合物的结构。将在最佳显色条件下拟定的分析方法用于合金钢中小量或痕量钼的测定,取得了满意的结果。 相似文献
24.
Described is the construction of a furanyl-cylcobutanone fragment suited for incorporation into a synthesis of the naturally occurring anti-cancer agent Providencin. 相似文献
25.
混合微乳液的增敏作用研究:Cd(Ⅱ)—5—Br—PADAP的分光光度测定 总被引:2,自引:0,他引:2
研究了在O/W混合微乳液SDS-OP/nC4H9OH/n-C7H16/H2O介质中,Cd(Ⅱ)-5-Br-PADAP的显色反应。结果表明显色反应的灵敏度较单一的SDS微乳液,单一的OP的微乳液,混合SDS-OP胶束的介质中,具有更好的增敏作用和稳定性,Cd浓度在0-5μg/100mL范围内符合比尔定律。方法用于废水和环境水样中微量Cd的测定,结果满意。 相似文献
26.
分光光度法测定甲基托布津含量的研究 总被引:1,自引:0,他引:1
基于甲基托布津与Cu^2 在氨水中发生络合反应,生成沉淀,再经离心分离后,移取上清液,通过与显色剂5-Br-PADAP在乳化剂OP增敏作用下显色后,用分光光度法测定,建立了测定甲基托布津含量的新方法。该方法灵敏度高,检出限低,检出范围为(0-3.1mg/25mL),并做了回收率实验,结果令人满意。 相似文献
27.
The hexamethylenetetramine/trifluoroacetic acid system was demonstrated to be capable of introducing three aldehyde groups into the phenol molecule. Facile, one-step procedures were developed for the preparation of hitherto difficult to synthesize 2-hydroxy-1,3,5-benzenetricarbaldehyde starting from either phenol or 4-hydroxybenzaldehyde. New pKa measurements showed 2-hydroxy-1,3,5-benzenetricarbaldehyde to be an acid stronger than previously reported. 相似文献
28.
We herein report simple and efficient methods for the synthesis of various formyl derivatives of dibenzofuran. The aldehydes reported are prepared in at most three steps and in yields greater than 60% from commercially available dibenzofuran, with one exception where isomers must be separated. The protocols described involve either formylation of previously functionalized dibenzofuran derivatives or the initial introduction of the formyl group and subsequent further functionalization under standard reaction conditions as described. We have also reported an efficient and simple method for the synthesis of key methoxydibenzofurans in high yield (65% overall for two steps). 相似文献
29.
Biswanath Das Katta Venkateswarlu Maddeboina Krishnaiah Harish Holla Anjoy Majhi 《Helvetica chimica acta》2006,89(7):1417-1421
Treatment of Baylis–Hillman adducts 1 with bromo(dimethyl)sulfonium bromide, Br(Me2)S+Br?, in MeCN was found to stereoselectively afford (Z)‐ and (E)‐allyl bromides 2 . The reaction is rapid at room temperature, high‐yielding, and highly stereoselective. 相似文献
30.
Preparation of Halogeno Pyridine Rhenates(III), [ReX6?n(Py)n](3?n)? (X = Br, Cl; n = 1?3) Crystal Structures of trans-[(C4H9)4N][ReBr4(Py)2], mer-[ReCl3(Py)3], and mer- [ReBr3(Py)3] The mixed halogeno-pyridine-rhenates(III), [ReX6?n(Py)n](3?n)? (X = Br, Cl), n = 1?3, have been prepared for the first time by reaction of the tetrabutylammoniumsalts (TBA)2[ReX6] (X = Br, Cl) in pyridine with (TBA)BH4 and separation by chromatography on Al2O3. Apart from the monopyridine complexes only the trans and mer isomers are formed from the bis-and tris-pyridine compounds. The X-ray structure determinations of the isotypic neutral complexes mer- [ReX3(Py)3] (monoclinic, space group P 21/n, Z = 4; for X = Cl: a = 9,1120(8), b = 12,5156(14), c = 15,6100(13) Å, β = 91,385(7)°; for X = Br: a = 9,152(5), b = 12,852(13), c = 15,669(2) Å, β = 90,43(2)°) reveal, due to the stronger trans influence of pyridine compared with Cl and Br, that the Re? X distances in asymmetric Py? Re? X3 axes with ReCl3 = 2,397 Å and ReBr3 = 2,534 Å are elongated by 1,3 and 1% in comparison with symmetric X1? Re? X2 axes with ReCl1 = ReCl2 = 2,367 Å and ReBr1 = 2,513 and ReBr2 = 2,506 Å, respectively. The Re? N bond lengths are roughly equal with 2,12 Å. Trans-(TBA)[ReBr4(Py)2] crystallizes triclinic, space group P1 , a = 9,2048(12), b = 12,0792(11), c = 15,525(2) Å, α = 95,239(10), β = 94,193(11), γ = 106,153(9)°, Z = 2. The unit cell contains two independent but very similar complex anions with approximate D2h(mmm) point symmetry. 相似文献