Structure elucidation and NMR assignments of a new dihydrochalcone from Empetrum nigrum subsp. asiaticum (Nakai ex H.Ito) Kuvaev

Abstract

A new dihydrochalcone, namely 2',5'-dimethyl-3'-methoxy-4',6'-dihydroxyl-dihydrochalcone (1) together with five known compounds were isolated from the CHCl₃ extract from Empetrum nigrum L. var. japonicum K. Koch (E. nigrum). The structures of 1 was elucidated by spectroscopic methods, including UV, IR, HR-ESI-MS and extensive 1D and 2D NMR techniques.     

Regioselective hydrosilations. II. The synthesis of silicon–hydrogen functional compounds

The discovery that the rhodium-catalyzed hydrosilation of unsaturated epoxides with compounds containing two Si? H functional groups proceeds in a discrete, stepwise fashion, has made possible the synthesis of a series of interesting compounds containing both Si? H and epoxy groups in the same molecule. These compounds can be used both as an interesting new class of epoxy monomers as well as intermediates for the preparation of a wide variety of novel monomers which incorporate epoxide as well as other types of polymerizable functional groups © 1993 John Wiley & Sons, Inc.     

Cover Picture: Palladium‐Catalyzed Carbon–Carbon Bond Formation and Cleavage of Organo(hydro)fullerenes (Chem. Eur. J. 19/2009)

An unexpected C? H bond dimerization reaction and C? C bond‐cleavage reaction in organo(hydro)fullerenes have been discovered. In their Communication on page 4760 ff. , K. Itami and M. Nambo describe the use of Pd catalysts for a number of interesting reactions of such fullerenes.

     

对氯硝基苯吸附在银纳米粒子上的偶联反应

表面增强拉曼光谱(SERS)具有极高的检测灵敏度, 通过检测吸附分子的SERS信号, 可以获得表面吸附分子的结构以及可能发生的反应. 在拉曼激发光源的辐射下, 在碱性溶液中, 银纳米粒子表面吸附的对氯硝基苯(PCNB)的SERS光谱与其固体的常规拉曼光谱相比, 出现异常SERS谱. 通过采用密度泛函理论(DFT)计算, 对PCNB以及可能的偶联产物p,p''-二氯偶氮苯(DCAB)进行理论分析以及谱峰归属, 发现这些异常峰来自其偶联产物DCAB的偶氮C－N＝N－C基团的基频振动.     

Bildung siliciumorganischer Verbindungen. 111. Die Hydrierung Si-chlorierter,C-spiroverbrückter 2,4-Disilacyclobutane mit LiAlH4 und iBu2AlH. Der Zugang zum Si8C3H20

Formation of Organosilicon Compounds. 111. The Hydrogenation of Si-chlorinated, C-spiro-linked 2,4-Disilacyclobutanes with LiAlH₄ or iBu₂AlH. The Access to Si₈C₃H₂₀ The hydrogenation of Si-chlorinated, C-spiro-linked 2,4-disilacyclobutanes containing C(SiCl₃)₂ terminal groups with LiAlH₄ in Et₂O proceeds under complete cleavage of the fourmembered rings and under elimination of one SiH₃ group. Such, Si₈C₃Cl₂₀ 4 forms (H₃Si)₂CH? SiH₂? CH(SiH₃)? SiH₂? CH(SiH₃)₂ 4 α, and even Si₈C₃H₂₀ 4a with LiAlH₄ forms 4 α. The hydrogenation of related compounds containing however CH(SiCl₃) terminal groups similarly proceeds under ring cleavage but no SiH₃ groups are eliminated. Such, (Cl₃Si)CH(SiCl₂)₂CH(SiCl₃) 41 forms (H₃Si)₂CH? SiH₂? CH₂(SiH₃) 41 α. However, in reactions with iBu₂AlH in pentane neither the disilacyclobutane rings are cleaved nor are SiH₃ groups eliminated. Only by this method Si₈C₃H₂₀ is accessible from 4 , Si₆C₂H₁₆ 3a from Si₆C₂Cl₁₆ 3 and Si₄C₂H₁₂ 41a from 41 . C(SiCl₃)₄ cleanly produces C(SiH₃)₄. Based on the knowledge about the different properties of LiAlH₄ and iBu₂AlH in hydrogenation reactions of disilacyclo-butanes it was possible to elucidate the composition and the structures of the hydrogenated derivatives of the product mixture from the reaction of MeCl₂Si? CCl₂? SiCl₃ with Si(Cu) [1] and to trace them back to the initially formed Si chlorinated disilacyclobutanes Si₆C₂Cl₁₅Me 34 , Si₆C₂Cl₁₄Me₂ 35 , Si₈C₃Cl₁₉Me 36 and Si₈C₃Cl₁₈Me₂ 37 . Compound 4a forms colourless crystals of space group P1 with a = 799.7(6), b = 1263.6(12), c = 1758.7(14) pm, α = 103.33(7)°, β = 95.28(6)°, γ = 105.57(7)° and Z = 4.