The Diels-Alder Reaction of 2,3-Disulfur-Substituted 1,3-Butadienes

The 2,3-disulfur-substituted 1,3-dienes (1) can be readily prepared from their stable 3-sulfolene precursors (2) by thermal extrusion of SO₂. The Diels-Alder reaction of diene (1) with several dienophiles has been studied. The substituent effect on the reactivity and regioselectivity follows the order of PhS >PhSO >PhSO₂. Lewis acid can greatly increase the regioselectivity of this reaction. The diene (1c), bearing a strong electron-withdrawing sulfonyl group, also reacted as a dienophile.     

氧化偶联反应和酸催化反应制备活性买麻藤醇二聚体衍生物

以天然得到的买麻藤醇为原料,以FeCl3 6H2O为氧化剂进行氧化偶联反应和酸催化二聚反应,获得了2个新的买麻藤醇二聚体及一个新的苯基萘衍生物:4-[1-(2,6-二羟基苯基)-2-(3,5-二羟基苯基)乙基]-2-[(1E)-2-(3,5-二羟基苯基)乙烯基]-1,3-苯二醇(1),2-[1-(2,6-二羟基苯基)-2-(3,5-二羟基苯基)乙基]-5-[(1E)-2-(2,6-二羟基苯基)乙烯基]-1,3-苯二醇(2)和4-(6,8-二甲氧基-2-萘基)-1,3-苯二醇(3).应用波谱分析的方法确定了它们的结构,并分别讨论了它们可能的形成机理.其中,化合物1和2首次为人工合成的二苯乙烯链状二聚体.活性测试结果表明,化合物1,2和3显示有较强的抗氧化活性,其IC50值分别为6.29×10-9,4.19×10-6和2.96×10-5mol L-1;化合物2还显示有较强的抗炎活性.     

激光促进乙醇氧化偶联表面反应机理

利用红外光谱（IR）和激光促进表面反应（LSSR）等技术，研究了沉淀法制得Cu2（PO4）（OH）表面上的乙醇氧化偶联合成1，4-丁二醇激光表面反应机理，结果表明：固体表面键激发是激光表面反应的有效激发模式; 乙醇在固体表面材料上的特定化学吸附态形式（－P＝O…H－CH2CH2OH）决定了反应产物的高选择性；固体材料表面晶格氧参与反应是使标题反应能够实现的一个重要因素．     

Reactivity of N-Phenyl-1-Aza-2-Cyano-1,3-Butadienes in the Diels-Alder Reaction

It is found that N-phenyl-2-cyano-1-azadiene 4, prepared via a two-step, one-pot, sequence from acrylanilide, undergoes efficient [4 + 2] cycloaddition with a complete range of electron rich, electron poor, and neutral dienophiles under remarkably mild thermal conditions (90-120 degrees C for 20-48 h). Regiospecific formation of the alpha-cycloadduct wherein the dienophile substituent is alpha to nitrogen is observed for vinyl ethers and styrene, whereas the Diels-Alder reactions with methyl acrylate and methyl vinyl ketone (MVK) produce alpha/beta mixtures in which the alpha-cycloadduct is the major regioisomer (approximately 4-5:1). An essentially identical reaction pattern was observed in the Diels-Alder reaction of N-(p-methoxyphenyl)-2-cyano-1-azadiene 18 and the 4-methyl-substituted azadiene 27. For compound 19 derived from cycloaddition of 18 with ethyl vinyl ether, facile conversion to the dihydropyridine 21 through loss of EtOH on brief acid treatment was also noted. The 2,4-cis-disubstitution pattern confirmed by X-ray diffraction for the major cycloadduct 29 isolated from the reaction of 27 with styrene provides evidence for the endo mode of cycloaddition in the Diels-Alder reaction of N-phenyl(aryl)-2-cyano-1-azadienes. Calculation of the frontier orbital energies and coefficients, as well as the transition state geometries for the [4 + 2] cycloaddition of N-phenyl-2-cyano-1-azadiene 4 with methyl vinyl ether, styrene, and MVK were carried out at the RHF AM1 level (MOPAC, Version 5.0). The FMO treatment indicates that the reaction of 4 with methyl vinyl ether occurs under LUMO(diene) control, whereas in contrast, the corresponding cycloaddition with MVK occurs preferably under HOMO(diene) control. A high degree of asynchronicity is observed in the calculated transition states for reaction of 4 with the three representative dienophiles. In all cases the transition states leading to the alpha-cycloadducts are lower in energy than those giving the beta-products. However, at the AM1 level the exo cycloaddition mode is found to be the preferred, this result contrasting with experimental results for azadiene 27.     

1,1′-联萘化合物的氧化偶联合成

评述了β-萘酚序列化合物在铜胺络合物、硫酸铜、铁盐、氧钒络合物等作用下,直接氧化偶联合成1,1′-联萘化合物的路线,讨论了反应机理.     

Synthesis of 4-Alkenylated Pyrazolinones by 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ)-Mediated Oxidative Coupling Reaction

1,3-Diarylpropenes firstly serve as efficient alkenylated reagents for the functionalization of pyrazolinones. In the presence of 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), it undergoes oxidative coupling and final dehydrogenation to give the highly substituted E,E-α,β,γ,δ-dienpyrazolinones in moderate to excellent yields.     

Synthesis and Properties of 2,3-Diethynyl-1,3-Butadienes

The first general preparative access to compounds of the 2,3-diethynyl-1,3-butadiene (DEBD) class is reported. The synthesis involves a one-pot, twofold Sonogashira-type, Pd⁰-catalyzed coupling of two terminal alkynes and a carbonate derivative of a 2-butyne-1,4-diol. The synthesis is broad in scope and members of this structural family are kinetically stable enough to be handled using standard laboratory techniques at ambient temperature. They decompose primarily through heat-promoted cyclodimerizations, which are impeded by alkyl substitution and accelerated by aryl or alkenyl substitution. An iterative sequence of these unprecedented Sonogashira-type couplings generates a new type of expanded dendralene. A suitably substituted DEBD carrying two terminal alkyne groups undergoes Glaser–Eglinton cyclo-oligomerization to produce a new class of expanded radialenes, which are chiral due to restricted rotation about their 1,3-butadiene units. The structural features giving rise to atropisomerism in these compounds are distinct from those reported previously.     

Oxidative Coupling of 1,3-Dicarbonyl Compounds by Cerium(IV) Ammonium Nitrate

A fast, mild, and highly efficient method for the intermolecular coupling of 1,3-dicarbonyl compounds using cerium ammonium nitrate in CH₃CN/CH₃OH/H₂O has been described. The procedure provided a convenient method for the synthesis of 1,4-diketone derivatives with excellent yields (up to 96%) and powerful evidence for the oxidation mechanism mediated by cerium ammonium nitrate.     

β—二羰基化合物的电解氧化偶联反应

β┐二羰基化合物的电解氧化偶联反应朱洪友张成敏刘复初＊（云南大学化学系昆明６５００９１）关键词β－二羰基化合物，电氧化，偶联反应１９９７－０６－０４收稿，１９９７－１２－１０修回云南省应用基础研究基金资助项目在有机合成上，β－二羰基化合物的偶联是形成...     

Comparison of Oxidative Aromatic Coupling and the Scholl Reaction

Does the dehydrogenative coupling of aromatic compounds mediated by AlCl₃ at high temperatures and also by FeCl₃, MoCl₅, PIFA, or K₃[Fe(CN)₆] at room temperature proceed by the same mechanism in all cases? With the growing importance of the synthesis of aromatic compounds by double C? H activation to give various biaryl structures, this question becomes pressing. Since some of these reactions proceed only in the presence of non‐oxidizing Lewis acids and some only in the presence of certain oxidants, the authors venture the hypothesis that, depending on the electronic structure of the substrates and the nature of the “catalyst”, two different mechanisms can operate. One involves the intermediacy of a radical cation and the other the formation of a sigma complex between the acid and the substrate. The goal of this Review is to encourage further mechanistic studies hopefully leading to an in‐depth understanding of this phenomenon.     

激光促进甲醇氧化偶联表面反应的规律

用沉淀法制备了Ｌｉ３ＰＯ４、ＢｉＰＯ４和Ｌｉ３ＰＯ４、ＢｉＰＯ４三种固体表面材料,并用ＸＲＤ、ＩＲ、ＴＰＤ和激光促进表面反应（ＬＳＳＲ）等技术研究了这些固体表面上甲醇氧化偶联生成乙二醇的反应规律。实验结果表明：甲醇在固体材料表面的Ｐ＝９键上产生Ｃ－Ｈ端的分子态吸附,在表面的Ｌｅｗｉｓ酸位（金属离子）上产生解离态吸附。Ｌｉ３ＰＯ４和ＢｉＰＯ４的相互作用可促进甲醇在固体表面上的分子态吸附而抑制解离态吸