O-Trimethylsilylenol ethers as versatile building blocks in a modular preparation of polyenic backbone

Versatility and synthetic potential of 1-(trimethylsilyloxy)-1,3-butadiene, 1-(trimethylsilyloxy)penta-1,3-diene, and their methyl substituted derivatives have been demonstrated in a modular synthetic methodology of stereodefined π-conjugated unsymmetrical, symmetrical two-dimensional, and octupolar polyenal structure.     

A Facile Route to Unsymmetrical Sulfide

Unsymmetrical sulfides can be generated by the reaction of chlorine substituted aromatic compounds in sulfoxide in the presence of fluorine anion in fair yield.A likely mechanism was proposed.     

Copper(II)/Palladium(II) catalysed highly selective cross-coupling of terminal alkynes in supercritical carbon dioxide

An efficient protocol for the synthesis of unsymmetrical 1,3-diynes was developed using supercritical carbon dioxide (ScCO₂) as the solvent. The direct coupling of two different terminal alkynes is catalysed by a bimetallic catalyst, CuCl₂·2H₂O/Pd(NH₃)₄Cl₂·H₂O, in the presence of the base tetramethylethylenediamine (TMEDA) and O₂. In pure ScCO₂, our bimetallic catalytic system maintains high activity over a wide substrate scope to provide unsymmetrical 1,3-diynes in good to excellent yields. In the proposed reaction mechanism, the synergistic cooperation between copper(II) and palladium(II) centres is responsible for the superior selectivity of the cross-coupling.     

纳米分子筛LTA包裹Ni-Salen配合物为修饰碳糊电极用于电催化氧化肼反应

采用柔性配体法将Ni-salen配合物包裹在纳米分子筛LTA的超笼中,用来修饰碳糊电极制得Ni(Ⅱ)-SalenA/CPE,并采用循环伏安法、计时电流法和计时库仑法考察了该电极电催化氧化0.1 mol/L NaOH溶液中肼反应性能.首先采用无有机模板剂法合成纳米分子筛LTA,并用各种技术进行了表征.XRD和粒径分析结果分别显示LTA晶体的平均粒径为56.1和72nm.在Ni(Ⅱ)-SalenA/CPE电极氧化还原位上水合肼催化氧化反应电子转移系数为0.64,速率常数为1.03×105cm3/(mol·s).电催化反应机理研究表明,水合肼氧化反应通过它与Ni3+(Salen)O(OH)反应或直接进行电氧化反应.阳极峰电流与扫描速率的平方根呈线性关系,表明反应受扩散控制,水合肼的扩散系数为1.18×10?7cm2/s.结果表明,Ni(Ⅱ)-SalenA/CPE对水合肼氧化反应表现出高的电催化活性,这是由于纳米分子筛LTA的多孔结构以及Ni(Ⅱ)-Salen的存在.最后研究了水合肼在碱性溶液中Ni(Ⅱ)-SalenA/CPE电极上的氧化反应机理,发现其为四电子过程,第一个电子转移反应为速率控制步骤,然后是一个三电子过程,产生环境友好的最终产物氮气和水.     

An efficient solvent free catalytic oxidation of sulfides to sulfoxides with hydrogen peroxide catalyzed by a binaphthyl-bridged Schiff base titanium complex

A titanium binaphthyl-bridged Schiff base complex proved to be an efficient catalyst for the hydrogen peroxide oxidation of aromatic and aliphatic sulfides to the corresponding sulfoxides in satisfactory yields under solvent-free conditions.     

Voltammetric determination of pyridoxine (Vitamin B6) at a carbon paste electrode modified with vanadyl(IV)-Salen complex

The preparation and electrochemical characterization of a carbon paste electrode modified with the N,N-ethylene-bis(salicylideneiminato)oxovanadium(IV) complex [VO(Salen)] as well as its behavior in relation to the oxidation of pyridoxine (Vitamin B₆) are described. The electrochemical behavior of the modified electrode and the electrooxidation of pyridoxine were investigated using cyclic voltammetry. The best voltammetric response was obtained for an electrode composition of 15% (m/m) [VO(Salen)] in the paste, KCl solution of pH 5.5-8.0 and scan rate of 25 mV s⁻¹. A sensitive linear voltammetric response for pyridoxine was obtained in the concentration range of 4.5×10⁻⁴ to 3.3×10⁻³ mol l⁻¹ with a slope of 42.5 μA mmol⁻¹ l, and a detection limit (3σ/slope) of 3.7×10⁻⁵ mol l⁻¹ using linear sweep voltammetry. Among several compounds tested only Vitamin B₁ seems to interfere in the analyte signal. The concentrations of pyridoxine in pharmaceutical formulations using the proposed electrode and an official spectrophotometric method based in the reaction with N,N-diethyl-p-phenylenediamine are in agreement at the 95% confidence level and within an acceptable range of error.     

A Novel Method of Preparing Unsymmetrical Thioether from Disulfides

The disulfides reacted with zinc in DMF, followed by alkyl halides, giving unsymmetrical thioether in excellent yields. This reaction takes place under mild and neutral conditions.     

Synthesis of new unsymmetrical polyarylester dendrimers

Preparation of polyarylester dendrimers containing 2-(hydroxymethyl)-1,4-butanediol and 2,2-bis(hydroxymethyl)-1,4-butanediol cores is described. These polyarylester dendrimers are unsymmetrical with respect to chain lengths and function as model systems for studying in vitro controlled drug release systems. Reaction conditions for deprotection of trichloroethyl group of the dendritic wedges have been improved.     

(S)-(+)-2,2-二甲基环丙烷甲酰胺的不对称合成

以环己二胺作为手性源,与3,5-二叔丁基水杨醛经缩合反应制得Salen配体(R,R)-N,N'-二(3,5-二叔丁基水杨醛)-1,2-环己二胺(6);甘氨酸乙酯盐酸盐经重氮化和6与三氟甲烷磺酸亚铜催化的不对称环丙烷化反应制得(S)-(+)-2,2-二甲基环丙烷甲酸乙酯(9);9经水解、酰氯化和氨解反应合成了(S)-(+)-2,2-二甲基环丙烷甲酰胺,ee值82%,总收率55.4%,其结构经1H NMR和IR确证。     

Acid-functionalized dissymmetric salen ligands and their manganese(III) complexes

Acid-functionalized symmetric and dissymmetric salen-type ligands were synthesized via a novel self-protection step in a quantitative yield. This synthetic method allows one to quickly prepare salen-based dissymmetric chiral compounds with tailorable coordinating properties. Therefore, this approach provides a blueprint for synthesizing and evaluating a new class of acid-functionalized salen ligands that can be used as chiral building blocks for a wide range of catalysts and coordination polymers with chemically tailorable properties.