六元含氮杂环润滑添加剂的摩擦学研究进展

对近年来三嗪类、喹唑啉类、磷嗪类等六元含氮杂环添加剂的摩擦学研究进行了概述,分析了其摩擦学机理及研究中存在的问题,并指出其未来发展应基础与应用研究并重,积极开展新型的、环境友好的六元含氮杂环润滑添加剂的研究。     

铁盐在杂环化合物合成中的应用

铁盐以其价廉易得、可持续、环境友好及后处理方便等特性已经广泛应用于许多反应中.综述了近年来铁盐在五和六元杂环化合物合成中的最新研究进展.     

具有生物活性的磷杂环化合物研究(Ⅸ)——Lawesson试剂与活泼氢的双官能团化合物的环化反应

研究Lawesson试剂与含活泼氢的双官能团化合物的环化反应,合成了O-P-O,N-P-S,N-P-N五元、六元型磷杂环。探讨了其成环可能性及其环化机理。初步的生物活性测定结果表明,应用Lawesson试剂所合成的磷杂环具有较好的除草活性。     

Fukui函数在传统杂环及单取代杂环亲电取代反应中的活性部位预测

采用收敛的Fukui 函数对传统杂环和其单取代产物在亲电取代反应中的活性部位做了预测。研究体系为传统的五元(呋喃、吡咯)和六元杂环(吡啶)以及取代基在邻位,间位和对位(相对于杂原子)的单取代杂环。计算结果显示在亲电取代反应中,其杂环中的杂原子可以看作间位定位基,其取代基的定位作用和杂原子的定位作用竞争来决定亲电进攻的活性部位,与实验和有机化学观念相一致。     

氮杂环有机催化CO2环加成反应：咪唑环的弱协同效应

稳定的CO₂ 需要高能分子的活化,如环氧化物。而亲核试剂有助于诱发三元氧环的开环,进而实现CO₂的插入活化。针对聚苯乙烯负载的有机催化剂,考察不同含氮杂环材料在催化CO₂环加成中的活性差异,发现五元氮杂环显示出了高于六元氮杂环的催化活性,五元氮杂环对底物间弱的协同效应是诱发环氧丙烷开环和活化CO₂插入的关键。进而与引入ZnCl₂、烷基胺的聚苯乙烯负载型催化剂作对比,虽然后两者反应速率得以提高,但也造成了选择性的下降。在无金属、无卤素、无添加剂、无溶剂下,PS-Im这种简单、廉价、稳定且可回收利用的聚苯乙烯负载氮杂环材料适合于工业推广。     

我国吡啶产业的发展动态

正吡啶(Pyridine)是苯环上含有一个氮原子取代后所形成的六元杂环化合物,是甲醛下游产品中的重要成员之一。吡啶应用广泛,称为杂环类三药及三药中间体的"芯片",深加工前景相当广阔,是我国亟待发展的精细与专用化学品之一。1发展现状我国吡啶生产始于1950年,已有63年的历史,     

新型吡啶基聚氨酯脲弹性体的热机械性能与介电性能

正吡啶及其衍生物是生物体系中重要的杂环化合物,是维生素B或植物中产生的生物碱中的结构元素。吡啶衍生物可用于农业、医药和其他行业。吡啶在六元芳环上具有氮杂环结构,其衍生物在杂环化学领域具有重要作用。许多天然产物中都发现有吡啶衍生物,但对于聚合物化学来说,则是通过不同方法合成了许多具有吡啶部分的化合物。基于吡啶的性质,对刚性吡啶杂环及其衍生物掺入聚合物基质进行了研究。吡啶环可以改善热稳定性和化学稳定性,保持高温下的机械性能,并改善电学和介电性能。因此获得了新型可     

1,3,3,5,7,7,——六硝基——1,5——二氮杂环辛烷的晶体与分子结构

关于四氮杂环辛烷类型化合物的结构以及结构和性能的关系研究较多,但是1,3,3,5,7,7,—六硝基—1,5,一二氮杂环辛烷(简称HDC)这类八元二氮杂化合物的结构在文献上还很少见。HDC八元环上有两个对称的N—硝胺和偕二硝基。要研究这类结构,探讨结构和性能间的关系,必须先了解分子构型、构象、堆积情况以及键长和键角等结构参数,为此采用X射线单晶衍射的方法测定了它的分子和晶体结构。     

六亚甲基亚胺的合成进展

六亚甲基亚胺是七元杂环亚胺类化合物,是多种有机产品重要的中间体,其合成方法有己内酰胺法、己二胺法、己二醇法、己二腈法等;国内外对其合成工艺和催化剂进行了广泛研究,其中最有影响力的是日本三菱油化所开发的连续化加氢工艺和钴合金催化剂.采用己内酰胺为原料是工业上生产六亚甲基亚胺的主要方法,但是己内酰胺极易聚合,反应转化率低,而且已有的金属催化剂寿命较短,选择性不高,所以其技术关键就是选择合适的催化剂.     

含噻吩的扩展六元卟啉的合成及其光谱性质研究

本文采用经过改进的Ulman卟啉合成方法制备了两种含有噻吩环的四元和六元卟啉衍生物。通过核磁共振氢谱、高分辨质谱等测试确定了化合物的结构。利用紫外-可见光谱对两种不同结构卟啉的光谱性质进行了研究,结果表明,与普通四吡咯卟啉相比,噻吩环取代吡咯而生成的杂环卟啉具有红移的紫外吸收,而扩展杂环卟啉Q带吸收已进入近红外区域,且强度也有所增加。     

Metal- and nonmetal-catalyzed synthesis of five-membered S,N-heterocycles

Due to significant biological activity associated with N-, O- and S-heterocycles, a number of reports for their synthesis have appeared in recent decades. The metal- and nonmetal-catalyzed synthesis of heterocycles is becoming an important and highly rewarding protocol in organic synthesis. This review summarizes the applications of metal and nonmetal as a catalyst for the synthesis of sulfur- and nitrogen-containing heterocycles. It describes the formation of five-membered heterocyclic rings.     

The Current Status of O‐Heterocycles: A Synthetic and Medicinal Overview

O‐Heterocycles have been explored in the field of medicinal chemistry for a long time, but their significance has not been duly recognised and they are often shunned in favour of N‐heterocycles. The design of bioactive molecules for nearly every pathophysiological condition is primarily focused on novel N‐heterocycles. The main reasons for such bias include the ease of synthesis and possible mimicking of physiological molecules by N‐heterocycles. But considering only this criterion rarely provides breakthrough molecules for a given disease condition, and instead the risks of toxicity or side effects are increased with such molecules. On the other hand, owing to improved synthetic feasibility, O‐heterocycles have established themselves as equally potent lead molecules for a wide range of pathophysiological conditions. In the last decade there have been hundreds of reports validating the fact that equally potent molecules can be designed and developed by using O‐heterocycles, and these are also expected to have comparably low toxicity. Even so, researchers tend to remain biased toward the use of N‐heterocycles over O‐heterocycles. Thus, this review provides a critical analysis of the synthesis and medicinal attributes of O‐heterocycles, such as pyrones, oxazolones, furanones, oxetanes, oxazolidinones, and dioxolonones, and others, reported in the last five years, underlining the need for and the advantages guiding researchers toward them.     

Ozonation of Aqueous Solutions of Nitrogen Heterocyclic Compounds : Benzotriazoles,Atrazine and Amitrole

Study of the ozonation of aqueous solutions of four heterocyclic nitrogen compounds, at slightly acidic pH in a heterogeneous gas-liquid system, showed that the reactivities of these compounds are different. Amitrole, a five-membered ring heterocycle, has been found to be a highly reactive compound, while atrazine, a six-membered ring heterocycle, has been found to be a poorly reactive compound. The benzotriazoles, benz-fused five-membered ring heterocycles, present intermediate reactivities. Moreovoer, the chemical natures of the ozonation by-products have been found to be different between amitrole and atrazine. With atrazine, ozone did not open the heterocyclic ring, and led to the formation of a trioxotriazine. With amitrole, ozone broke the heterocyclic ring and formed mainly formamide.     

Design and Synthesis of Polycyclic Imidazole‐Containing N‐ Heterocycles based on C?H Activation/Cyclization Reactions

A new strategy for the synthesis of polycyclic imidazole‐containing N‐heterocycles, based on the two general synthetic ways, namely the Pd(II)‐catalyzed intramolecular arylation via CH/C Hal and CH/CH coupling reactions, was developed. The method proposed here enables the synthesis of many fused N‐heterocycles containing purine, 1‐deazapurines and benzimidazole structural units.     

Palladium‐Catalyzed Cyclization Reactions of Acetylene‐Containing Amino Acids

Enantiomerically pure acetylene‐containing α‐amino acids were used as versatile starting materials for the synthesis of a variety of heterocycles via Pd‐mediated cyclization reactions. Depending on the protecting group strategy, both the carboxylate and the amine function of the amino acids could participate in the cyclizations, thus giving rise to oxygen heterocycles (α‐aminolactones) and nitrogen heterocycles (cyclic α‐amino acid derivatives), respectively. Beside the straightforward cyclization, cyclization/cross‐coupling reactions were also successfully carried out to provide the corresponding substituted cyclic amino acid derivatives.     

Synthesis of cyclic carbonates from urea and diols over metal oxides

Several metal oxides were used for synthesis of ethylene carbonate from urea and ethylene glycol. ZnO showed high activity towards the reaction. TPD, FTIR and reaction test indicated that the catalysts with appropriate acid and base properties were favorable to the synthesis of cyclic carbonate. Furthermore, the reaction of urea with various diols revealed that the selectivity of five-membered cyclic carbonates was higher than that of six-membered cyclic carbonates.     

Manifestations of stereoelectronic interactions in 1JC-H one-bond coupling constants

Two-electron/two-orbital hyperconjugative interactions depend on the relative orientation of bonds and lone pairs in a molecule and are also inversely proportional to the energy difference between the interacting orbitals. Spectroscopic manifestations of stereoelectronic interactions are particularly useful experimental signatures of these effects which can be utilized for testing molecular models. Empirical observations together with theoretical interpretations in cyclohexane and six-membered heterocycles confirm the relevance of sigma C-H ax --> sigma* C-H ax , n X --> sigma* C-H ax (X = O or N), sigma C-S --> sigma* C-H eq , beta-n O --> sigma* C-H eq , sigma C(2)-H ax --> pi* CY (Y = O, S, or CH 2), and sigma C(2)-H ax --> sigma* S-O ax two-electron/two-orbital stereoelectronic interactions that weaken the acceptor (or donor) C-H bonds and attenuate the Fermi contribution to the one-bond (13)C- (1)H coupling constants.     

Solid-phase synthesis of sulfur containing heterocycles

Solid-phase organic synthesis by combinatorial techniques is a widely exploited area in the discovery of new pharmacologically active compounds and is a rapidly expanding area of synthetic organic chemistry. Because of many biological activities possessed by heterocycles, a large number of reports related to their solid-phase synthesis have appeared in recent decades. In this review article, I have described the importance of solid-phase synthetic strategies for the synthesis of sulfur atom containing heterocycles.