Recent Progress

• 发表于 2013-03-13

  最新科研进展请参见实验室新闻 http://old.chem.pku.edu.cn/xizf/revised/news.php?size=100&lang=

• 发表于 2010-01-05

   

  研究室工作进展 January 6, 2010
   
  Isolation and X-ray Structure of a Trimeric 1,4-Dilithio-1, 3-butadiene and a Dimeric Me₃Si-substituted 1,4-dilithio-1,3-butadiene
   
  Lantao Liu, Wen-Xiong Zhang,* Qian Luo, Heng Li, and Zhenfeng Xi*
   
  Organometallics 2010, 29, 278-281.
   
  
   
   
  The X-ray crystallographic structures of a trimeric all-alkyl substituted 1,4-dilithio-1,3- butadiene with a Li₆ pseudooctahedron as well as of the dimeric Me₃Si-substituted 1,4-dilithio-1,3-butadiene with a Li₄ tetrahedron are reported.
   
  本工作背景介绍
  本研究小组自1999年发现1,4-双锂-1,3-丁二烯衍生物具有不同与常见单锂金属有机合成试剂的反应模式以来，一直努力建立合成该类衍生物纯品的有效方法，以便最终将这类衍生物发展成方便使用的双锂金属有机合成试剂；同时，我们希望了解该类双锂金属有机化合物尤其是全烷基取代的衍生物的结构与成键模式。经过几代研究生的努力，最终在2009年由刘澜涛同学在张文雄老师的指导下完成该工作，可以方便地以80%以上的分离收率获得克级以上多种衍生物的晶体（其中之一如图），并作为试剂方便地用于进一步的反应。
   
   
  Background of this work
  1,4-Dilithio-1,3-butadienes found by our group in 1999 demonstrate different reaction patterns from commonly widely used mono-Li reagents. Since then, we have tried to establish an efficient synthetic method to get pure compounds, aiming at developing such compounds as useful organo-di-lithio reagents. After many trials by several graduate students, this goal was finally achieved in 2009 by Mr. Lantao Liu and Dr. Wen-Xiong Zhang. Most of such derivatives now can be obtained in this group as fine crystalline compounds in over 80% isolated yields with gram-scale. The picture shows one of such derivatives, which are kept in cooler and used when needed.
• 发表于 2009-11-03

   

  研究室工作进展 Nov. 1, 2009
   
  One-pot Multicomponent Synthesis of Azaindoles and Pyrroles from One
  Molecule of a Silicon-Tethered Diyne and Three or Two Molecules of
  Organonitriles Mediated by Zirconocene
   
  Shaoguang Zhang, Xiaohua Sun, Wen-Xiong Zhang, and Zhenfeng Xi*
   
  Chem. Eur. J. 2009, ASAP online October 31
   
   
   
  A zirconocene-mediated one-pot multi-component synthesis process has been developed, leading to the synthesis of 5-azaindoles and pyrrole derivatives, from a Si-tethered diyne and three or two different or identical organonitriles. 5-Azaindoles and pyrrole derivatives of diversified structures and substitution patterns could be highly selectively prepared via this protocol. A wide variety of organonitriles and Si-tethered diynes, either aliphatic or aromatic with both electron-withdrawing groups and electron-donating groups, could be used to afford 5-azaindoles and/or pyrroles in good-to-excellent isolated yields. A key intermediate formed in the Cp₂Zr(II)-mediated reaction of one (PhC≡C)₂SiMe₂, two molecules of i-PrCN and one p-TolylCN was characterized by X-ray single-crystal structural analysis, which has allowed us to gain a good understanding of the reaction process.
• 发表于 2009-09-10

   

  Hydride-induced Novel Cyclization of Dienedinitriles Leading to Multi-functionalized Cyclopentadienes
   
  Hui-jun Zhang, Tianhao Meng, Bernard Demerseman, Christian Bruneau* and Zhenfeng Xi*
  Org. Lett. 2009, ASAP online.
   
   
   

  　　By treatment with LiAlH₄, 1,4-dicyano-1,4-bis(trimethylsilyl)-1,3-dienes underwent a novel hydride-induced nucleophilic intermolecular 1,4-addition to the a, b-unsaturated nitrile moiety, followed by an immediate nucleophilic intramolecular 1,2-addition to the remaining CN group, to afford multiply functionalized cyclopentadienes in high isolated yields. These multi-functional (-CN, -NH₂, -SiMe₃, -H) cyclopentadienes are of a rich and interesting reaction chemistry as preliminarily demonstrated by their reaction with ArNCO involving both the substituent and the ring.

• 发表于 2009-09-10
  Isolation, Structural Characterization, and Synthetic Application of Oxy-cyclopentadienyl Dianions
   
  Lantao Liu, Wen-Xiong Zhang, Chao Wang, Congyang Wang, and Zhenfeng Xi*
  Angew. Chem. Int. Ed. 2009, 48, in press.
   
   
   
  Isolation and applications of OCp: Novel cyclic dianions, lithio oxycyclopentadienyl dianions were isolated in high yields and structurally characterized by X-ray single crystal structural analysis. Interesting reaction chemistry and useful synthetic applications of these cyclic dianions were demonstrated to afford cyclopentadienes or transition-metal complexes.
  Cyclic dianions are very important synthetically useful intermediates for construction of organic compounds and organometallic complexes. However, synthetic methods and structural information for cyclic dianions are very much limited.
  This paper reports the first isolation and X-ray structural characterization of novel oxy-cyclopentadienyl (OCp for short) dianions generated via a concise reaction of 1,4-dilithio-1,3-butadienes with CO. The concomitance of the CpLi moiety, the exocyclic oxy anion, and those multi-reactive sites makes such dianion species structurally very unique and of novel reaction chemistry.
• 发表于 2009-09-10
  Skeletal Rearrangement of All-carbon Spiro Skeletons
  Mediated by Lewis Acid
   
  Fei Zhao, Chao Wang, Lantao Liu, Wen-Xiong Zhang, and Zhenfeng Xi*
  Chem. Commun. 2009, ASAP online.
   
   
   
   　　Mediated by AlCl₃, substituted spiro[4.5]deca-tetraenesunderwent novel and selective skeletal rearrangement to generate indene derivatives in high to excellent yields.Selective cleavage of C-C and C-H bond is of great importance both fundamentally and practically. Sequential cleavage of both C–C and C–H bonds in all-carbon cyclic compounds spiro[4.5]deca-tetraenes was achieved to generate indene derivates via a novel AlCl₃-mediated process.

  　　This work has the following two features. (1) First example on the cleavage of C-C and C-H bond of all-carbon spiro compounds; (2) A new protocol on cleavage of C-C and C-H bond.

• 发表于 2009-09-10

   

  Zirconium- and Silicon-Containing Intermediates with Three Fused Rings in a Zirconocene-Mediated Intermolecular Coupling Reaction
   
  Wen-Xiong Zhang, Shaoguang Zhang, Xiaohua Sun, Masayoshi Nishiura,
  Zhaomin Hou,* and Zhenfeng Xi*
  Angew. Chem. Int. Ed. 2009, 48, 7227-7231.
   
   
   
  Veritable Jack-in-the-box: The isolation and characterization of key Zr/Si-containing intermediates was achieved for a zirconocene-mediated intermolecular coupling reaction (see scheme). The fate of the various functional groups was determined, and the reactivity of intermediate with a variety of unsaturated substrates was also investigated.
  This work demonstrates that the isolation and reactivity investigation ofreactive organometallic intermediates are not only of importance and interest for the in-depth understanding of seemingly complicated reaction mechanisms,but can alsolead to the discovery of new synthetic methods.
• 发表于 2009-07-23

  Zirconocene-mediated ligand-switched selective cleavage of active and inert carbon-carbon bonds in allylcyclopropanes

  Chao Wang, Liang Deng, Jun Yan, Hailin Wang, Qian Luo, Wen-Xiong Zhang and Zhenfeng Xi^*
  Chem. Commun., 2009, 4414
   
   
  
   
  　　In this paper, we have developed a novel zirconium (II)-mediated ligand-controlled selective cleavage of different C–C bonds in bromoallylcyclopropane, which contains multiply reactive sites. This reaction represents a new way leading to selective cleavage of both reactive and inert C–C bonds.
   

  本论文主要研究了低价有机锆试剂促进的多取代环丙烷的开环反应。在反应中对锆的配体进行调控后，惰性的环丙烷侧链碳碳键可以被切断，而活泼的三元母环却可以保持。碳碳键活化以其重要性和高难度被称为化学的圣杯。本部分的工作初步体现了一类新型的碳碳键活化过程。
• 发表于 2009-05-31

  Synthesis of functionalized siloles from Si-tethered diynes

  Qian Luo, Li Gu, Chao Wang, Junhui Liu, Wen-Xiong Zhang and Zhenfeng Xi^*
  Tetrahedron Lett. 2009, 32, 3213-3215
  （Tetrahedron Letters 创刊五十周年纪念专集邀请论文）
   
   
   
   
  A new synthetic itinerary to silole from Si-tethered diynes is reported. In this protocol, the Si-tethered diyne manifests definitely the reactivity of monoyne to form the lithio silole via zirconacyclopetadiene, 1,4-diiodo-1,3-butadiene and the corresponding dilithiodiene successively. Lithio siloles thus obtained above could be easily functionalized to give various types of silole derivatives. Complex structure like bridged bis-silole compounds could also be constructed by this process.
   
  噻咯 (Silole)在材料化学研究领域非常重要。本文以硅桥连二炔为起始物发展了合成噻咯的新方法。硅桥连二炔以单炔的反应性通过锆杂环戊二烯，相应的1，4-二碘-1，3-丁二烯以及1，4-二锂-1，3-丁二烯这样的反应过程最终形成了锂代噻咯。锂代噻咯可以被很容易地进一步官能团化，从而形成不同的噻咯衍生物。通过此方法，可以得到用其它方法很难得到的结构复杂的桥连双噻咯化合物。
   

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• 发表于 2009-01-31

   

  Star-shaped Silacyclobutene-Containing π-Systems:
  Synthesis and Optical Properties
   
  Organometallics 2009, 28, 413-417
   
  
     Well-defined π-conjugated systems containing two or three silacyclobutene units have been synthesized in high yields via regioselective coupling of bis(phenylethynyl)silanes with dialkynylbenzene or trialkynylbenzene in the presence of Cp₂ZrBu₂. The UV-vis absorption and fluorescence spectra of these new π-conjugated systems have demonstrated that the increase in silacyclobutene units per molecule from two or three brings about an increase of the extinction coefficient.
    
   从单炔基苯、二炔基苯或三炔基苯以及二炔基硅烷出发，以较高产率合成了以苯为核、结构中含有一个、两个和三个硅杂环丁烯骨架的共轭有机硅分子。随着分子中硅杂环丁烯骨架的增加，这类化合物的紫外吸收与荧光效率均有显著的提高。