杂氮三环化学的进展

本文综述了含中心原子si、B、Ti、Al杂氮三环化学的进展。在合成工作的基础上利用各种手段着重研究了分子中N→M配位键的存在。研究表明配位键的强度不仅受取代基R的影响,而且还与环结构的变化有关。系统地采用X射线光电子能谱(XPS)技术对此类化合物的分子结构进行了研究。     

Structure and Bonding in Organometallic Anions of Heavy Group 14 and 15 Elements

Alkali metal organometallic complexes (containing C–metal bonds) and the frequently structrually related alkali metal amides and alkoxides have been investigated extensively both in the solid state and in solution in the past two decades. However, until recently, the related complexes containing the heavier metallic and semi-metallic p block elements and the alkali and alkaline earth metals had rarely been studied in their own right. Recent solid-state structural studies have illustrated the immense structural diversity and bonding modes to be found within these species. One of the principal focuses of recent studies has been complexes containing organometallic anions of p block metals (e.g., triorganostannates, containing R₃Sn^?) in which metal–metal bonds occur between the heavy p block metal and the alkali or alkaline earth metal and the investigation of the nature of this bonding. The development of new synthetic routes has also allowed the preparation of a variety of anionic ligands with p block metal centers which promise new opportunities in coordination chemistry. In addition, the synthesis of a family of homologous anionic π complexes has given a fresh direction in the chemistry of p block metal metallocene complexes.     

Synthesis of 2-[5-amino-2,3-dihydro-4H-imidazol-4-ylidene]malononitriles

Using the system of tetracyanoethylene, ammonium acetate and a carbonyl compound, the preparation of 2-[5-amino-2,3-dihydro-4H-imidazol-4-ylidene]malononitriles was carried out. The structures of these new dihydroimidazoles were determined by NMR experiments and by X-ray crystallography.     

Comparison of simultaneous distillation extraction and solid-phase microextraction for the determination of volatile flavor components

Traditional simultaneous distillation extraction (SDE) and solid-phase microextraction (SPME) techniques were compared for their effectiveness in the extraction of volatile flavor compounds from various mustard paste samples. Each method was used to evaluate the responses of some analytes from real samples and calibration standards in order to provide sensitivity comparisons between the two techniques. Experimental results showed traditional SDE lacked the sensitivity needed to evaluate certain flavor volatiles, such as 1,2-propanediol. Dramatic improvements in the extraction ability of the SPME fibers over the traditional SDE method were noted. Different SPME fibers were investigated to determine the selectivity of the various fibers to the different flavor compounds present in the mustard paste samples. Parameters that might affect the SPME, such as the duration of absorption and desorption, temperature of extraction, and the polarity and structure of the fiber were investigated. Of the various fibers investigated, the PDMS–DVB fiber proved to be the most desirable for these analytes.     

元素有机化合物在有机合成中的应用

本文简要介绍磷、硫、砷、硅、硼和锡有机化合物在有机合成应用中研究得较活跃的一些例子,并着重讨论应用元素有机化合物合成立体专一性、光学活性和生理活性的化合物。     

Synthesis of amine, halide, and pyridinium terminated 2-alkyl-p-tert-butylcalix[4]arenes

The synthesis of calix[4]arenes with functional groups tethered to a single methylene bridge has been explored. Mono-lithiated calix[4]arenes react with 1,ω-bromochloroalkanes to give 2-(ω-chloroalkyl)-calix[4]arenes, which function as key intermediates in the synthesis of a variety of tether-functionalized calix[4]arenes. Subsequent reactivity of these chloroalkyl species has allowed for successful synthesis of 2-(ω-iodoalkyl)-calix[4]arenes, 2-(ω-pyridiniumalkyl)-calix[4]arenes, and 2-(ω-aminoalkyl)-calix[4]arenes. This latter group of amine-terminated calix[4]arenes are especially significant as they may serve as useful entries to a wide range of subsequent chemistry, including metal coordination or attachment to a solid support. Both alkyl and aryl amines have been incorporated at the end of the tether, and a 2,6-diisopropylaniline derivative has been analyzed by X-ray diffraction.