Total syntheses of melinonine-E and strychnoxanthine: Evolution of the synthetic strategy enabled by novel method development

In this full account, the evolution of a synthetic strategy was detailed from a nitroso-ene cyclization to an aza-Wacker reaction for ring construction in the syntheses of melinonine-E and strychnoxanthine. The aza-Wacker cyclization to form the bridged ring was successfully developed and applied in the first asymmetric syntheses of melinonine-E and strychnoxanthine in 5–6 steps from a readily available chiral lactone. The proposed biogenesis of these two rare β-carbolinium alkaloids was revised based on their absolute configurations. Moreover, the substrate scope of the aza-Wacker cyclization demonstrated its potential for accessing various bridged ring skeletons. The mechanistic investigation established that the profound effect of the N-substituent on the amide was crucial to the success of the cyclization via the tunable amidopalladation pathway.     

α-Alkyl-α-aminosilanes: Synthesis via Alkylation and Hydrosilylation

The readily available aminomethylsilanes can be utilized to prepare the less available α-alkyl-α-aminosilanes. Versatile t-butoxy-carbonal (Boc) derivatives can be metalated between nitrogen and silicon, and then alkylated by an electrophile at this position. Two alternative procedures were also developed, including an aza-reverse-Brook rearrangement of metalated N-silylcarbamates and hydrosilylation of N-alkenylcarbamates. © 1997 by John Wiley & Sons, Ltd.     

The synthesis, spectroscopic, electrochemical and X-ray diffraction characterization of novel bridged ferrocene precursors for use in self-assembled monolayers

The synthesis of 1,6-diferrocenylhexane-1,6-dione (I), 1-ferrocenylcarbonyl-2-ferrocenylcyclopentene (II) and 1,6-diferrocenylhexane (III) is reported. All three compounds were characterized by ¹H NMR, ¹³C NMR, and infra-red spectroscopy, mass spectrometry, cyclic voltammetry and chronoamperometry. Compounds I and III each exhibit a single two electron transfer, while compound (II) exhibits two single electron transfers. Compounds (I) and (II) were further studied by single crystal X-ray diffraction. In compound (I), both carbonyl groups are in plane with the adjacent ferrocenyl Cp ring. For compound (II) one of the ferrocenyl Cp rings is coplanar with the carbonyl group, the other with the double bond of the cyclopentene ring, but the CO moiety and the double bond are basically perpendicular to each other.     

Bridged polyhedral oligomeric silsesquioxane (POSS): A potential member of silsequioxanes

Two novel and well-defined polyhedral oligomeric silsesquioxanes（POSS） with two same Si₈O₁₂ cores and a reactive NH group, namely bridged-POSS（2a and 2b）,have been prepared by the traditional ’corner-capping’ reaction.X-ray diffraction demonstrates that those two POSS have the similar T₈ structure.From the thermo-gravimetric analysis,bridged-POSS shows the belter thermal degradation stability than the contrastive POSS.     

三桥连双铁(Ⅲ)配合物[Fe2(IDB)2(O)(CH3CO2)2]Cl2·CH3OH的晶体结构及其傅立叶变换拉曼光谱

合成了一种新的三桥连双铁(Ⅲ)配合物[Fe2(IDB)2(O)(CH3CO2)2]Cl2·CH3OH,IDB为N,N'-di(2'-benzimidazolyl methyl) imine,利用单晶x射线衍射及其它谱学方法对所合成配合物进行了表征.每个双核单元的两个铁原子均通过一个氧原子和两个醋酸根连接,每个铁原子同时还与位于桥氧原子对位的三齿配体IDB重脂肪链上氮原子相结合,每个铁(Ⅲ)中心为一变形八面体结构.对该新化合物的拉曼光谱进行了研究并对一些谱峰进行了归属.     

超分子体系中的分子识别桥──连环糊精对模型底物的键合能力及分子选择性

综述了近年来桥连双环糊精分子识别的研究进展,主要从疏水相互作用、多重识别、尺寸和构型匹配、热力学性质以及环糊精二聚体分子识别的一些应用等方面对研究结果进行了评述.     

Thiacalix[4]arene derivatives with proximally bridged lower rim

New types of lower rim proximally bridged thiacalix[4]arenes have been prepared by direct aminolysis of starting tetraacetate derivative in the cone conformation using aliphatic α,ω-diamines. X-ray crystallography revealed the highly preorganized array of -C(O)NH- bonds resulting in strong intramolecular hydrogen bonding between amide groups of both bridges. The length of the corresponding diamine was found to have an essential influence on the yield of these bridged molecules.     

Synthesis and catalytic properties of hierarchical TS-1 in the presence of cationic organosilane surfactant

Hierarchical TS-1 has been synthesized in the presence of cationic organosilane surfactant.The material is characterized with XRD,TEM,N₂ adsorption isotherm.The results show that the hierarchical TS-1 aggregates consist of small primary units with sizes of 20-30 nm.The BET surface area increases from 420 to 513 m²/g compared to conventional TS-1 zeolite.The sample is shown to be more active in epoxidation of cyclohexene than conventional TS-1.     

Chiral Phosphoric Acid Catalyzed Asymmetric Hydrolysis of Biaryl Oxazepines for the Synthesis of Axially Chiral Biaryl Amino Phenol Derivatives

The development of catalytic asymmetric reaction with water as the reactant is challenging due to the reactivity- and stereoselectivity-control issues resulted from the low nucleophilicity and the small size of water. We disclose herein a chiral phosphoric acid (CPA) catalyzed atroposelective ring-opening reaction of biaryl oxazepines with water. A series of biaryl oxazepines undergo the CPA catalyzed asymmetric hydrolysis in a highly enantioselective manner. The key for the success of this reaction is the use of a new SPINOL-derived CPA catalyst and the high reactivity of biaryl oxazepine substrates towards water under acidic conditions. Density functional theory calculations suggest that the reaction proceeds via a dynamic kinetic resolution pathway and the CPA catalyzed addition of water to the imine group is both enantio- and rate-determining.     

1,2-双(四甲基环戊二烯基)四甲基二硅烷与六碳基钼的反应

1,2-双(四甲基环戊二烯基)四甲基二硅烷与正丁基锂作用生成(四甲基二硅撑)双(四甲基环戊二烯基负离子盐),后者随即与六碳基钼反应形成1,1'-(四甲基二硅撑)双(四甲基环戊二烯基铝负离子盐)-(Me₂SiSiMe₂)[Me₄CpMo(CO)₃-Li⁺]₂(I),I与冰醋酸作用,随即分别与CCl₄,NBS及I₂反应,生成相应的铝卤化合物(Me₂SiSiMe₂)[Me₄CpMo(CO)₃X]₂[X=Cl(1),Br(2),I(3)].I与CH₃I反应,在钼原子上发生烃基化,得到产物(Me₂SiSiMe₂)[Me₄CpMo(CO)₃Me]₂(4);I与单质I₂直接反应,生成脱硅桥产物Me₄Cp(CO)>₃I(5).经元素分析、IR及¹HNMR表征了化合物1-5的结构。