One-pot synthesis of novel pyrrolo-1,4-benzoxazines via a three- component reaction of 2-amino phenols,acetylenic esters and nitrostyrene derivatives简

A simple and efficient synthetic protocol has been developed using a one-pot, three-component reaction involving 2-amino phenols, dialkyl acetylene dicarboxylates and nitrostyrene derivatives. Utilizing this protocol, a variety of novel pyrrolo-1,4-benzoxazine derivatives were synthesized in excellent yields.     

A highly active catalyst for the reductive cyclization of ortho-nitrostyrenes under mild conditions

A mild and efficient method for the palladium-catalyzed reductive cyclization of ortho-nitrostyrenes to afford indoles is reported. Treatment of ortho-nitrostyrenes with 0.1 mol% palladium (II) trifluoroacetate [Pd(TFA)₂] and 0.7 mol% 3,4,7,8-tetramethyl-1,10-phenanthroline (tm-phen) in DMF at 15 psig CO and 80 °C afforded indoles in good to excellent yields. When the reaction was conducted in toluene, the corresponding N-hydroxyindole was isolated. A mechanism that accounts for the formation of N-hydroxyindole is proposed.     

β-芳基烯酰胺化合物的新合成方法

本文报道了一条简便合成烯酰胺类化合物的方法.在酸酐或酰氯的存在下,通过钛锌试剂还原硝基芳基乙烯类化合物一步生成芳基烯酰胺类化合物,并利用此法实现了天然产物Alatamide的合成.     

One-pot synthesis of pyrrolo[1,2-a]pyrazines via three component reaction of ethylenediamine, acetylenic esters and nitrostyrene derivatives

An effective route to pyrrolo[1,2-a]pyrazines is described via reaction of ethylenediamine,acetylenic esters and nitrostyrene derivatives in the presence of 20 mol%of sulfamic acid.     

Lipophilicity determination of some nitrostyrene derivatives on RP-2, PR-8 and RP-18 layers

Summary The lipophilicity of 33 nitrostyrene derivatives was determined by reversed-phase thin-layer chromatography on RP-2, RP-8 and RP-18 layers using methanol as the organic phase. The R_M value of each compound linearly decreased with increasing concentration of the organic solvent. The retention strength of RP-2 layer was lower than that of RP-8 and RP-18 layers. Between the retention strength of RP-8 and RP-18 layers no significant difference was detected. Minor differences among the selectivities of the layers were also observed. The impact of the change of methanol concentration on the retention was higher on RP-2 than on RP-18 layers probably due to the sterically favourable interaction of methanol with the shorter alkyl groups on the silica surface.     

金属载体强相互作用增强Au/TiO2催化剂在3-硝基苯乙烯选择性加氢反应的活性

自Haruta与Hutchings于上世纪八十年代末发现金纳米催化剂优异的反应活性以来,科研人员对金催化的应用领域进行了广泛而深入地研究.对金催化科学和应用领域的研究一直在进行.大量的研究表明,金催化剂在各种选择性氧化反应中具有优异的催化性能(高活性和高选择性).然而,在催化加氢反应中,尽管金催化剂相比于铂族金属显示出优越的选择性,但是由于金催化剂选择性加氢反应的活性较差,使其在选择性催化加氢反应中的应用受到了极大的限制.研究表明,金催化剂较弱的活化氢气能力是其催化加氢反应活性低的主要原因.研究发现,氢气活化的活性中心可能是界面、负价金、低配位的金原子等.金催化剂具有明显的载体效应,金属-载体之间的相互作用能够显著地改变金催化剂的催化性能.Tauster等研究发现,铂族金属与还原性载体之间存在强相互作用,能够引发载体包覆金属表面,并且使得电子从载体向金属迁移,导致金属带负电.受金属-载体强相互作用(SMSI)效应的启发,本文探究了Au/TiO2催化剂中SMSI对金催化剂加氢性能的影响.在H2或O2气氛下高温焙烧Au/TiO2,获得一系列金催化剂(Au/TiO2-TA,T为焙烧温度(oC):300、400、500和600;A为气氛:H2或O2).对比在3-硝基苯乙烯(3-NS)选择性加氢反应中的活性发现,Au/TiO2-500H的TOF值是Au/TiO2-500O的3.3倍;动力学测试表明,Au/TiO2-500H和Au/TiO2-500O的反应表观活化能分别为79.5和105.1 kJ/mol.这表明两类催化剂催化活性中心的结构存在差异.X射线光电子能谱测试结果表明,Au/TiO2-H样品中Au带部分负电,而Au/TiO2-O中Au显示为金属态.HAADF-STEM和EELS显示,Au/TiO2-H中Au NPs的表面有TiOx物种,增加了Au-TiO2的界面.EPR结果表明,Au/TiO2-H中存在表面Ti3+物种,而Au/TiO2-O样品中则没有.为确认加氢反应的活性中心到底是界面还是负价金物种,本文探究了不同温度下氢气处理的Au/TiO2的结构与性能的关系,发现Au/TiO2-300H/400H/500H催化剂都显示出较好的催化3-NS加氢活性,而Au/TiO2-600H虽然具有更多的负价金物种,但是3-NS选择性加氢反应的活性反而降低,因此,负价金不是活性中心.这是因为不同温度处理的Au/TiO2-H样品中,SMSI的强弱不同,在300、400、500 oC下,SMSI能够增加Au-TiO2的界面长度,从而增强了3-NS加氢反应的活性;而温度达到600 oC,SMSI效应太强,Au NPs被包覆更密实,导致Au/TiO2-600H的3-NS选择性加氢反应的活性下降.密度泛函理论计算表明,Au/TiO2-H样品具有更低的H2解离活化能以及氢转移活化能.氢氘交换反应也进一步验证了SMSI有利于H2的活化.     

An efficient, transition-metal-free process for the synthesis of substituted dihydrofurans via a Michael/cyclization tandem reaction

An efficient green route for the synthesis of substituted dihydrofurans was developed through a simple base-catalyzed, tandem reaction of nitrostyrene with 1,3-dicarbonyl compounds. The desired products were prepared with a large substrate scope and in excellent yields (up to 95%).