逆Diels——-Alder反应及其在有机合成中的应用

本文首先介绍了逆Diels—Alder反应的内容、形式及影响因素等,进而用反应实例阐明了逆Diels—Alder反应在有机合成中的重要作用,即类似保护基的作用、改变基团性能的作用和类似取代反应的作用。指出该反应在很大程度上扩充了Diels—Alder反应的应用,它能合成那些用其他方办难以得到的化合物。     

羰基保护及其在有机合成中的应用

论述了保护羰基的意义、保护方法和保护基种类以及在有机合成中的应用,给出了较多的应用实例,阐明保护羰基在有机合成中的重要性和必要性。     

钯试剂在含氮杂环化合物合成上的应用

近年来,有机合成化学和有机金属化学得到了突飞猛进的发展,其中发现很多过渡金属有机化合物,过渡金属盐及过渡金属本身。对杂环化合物骨架形成的反应中具有特殊的催化作用。因为在没有这些有效的有机过渡金属化合物作为催化剂时,在形成杂环化合物骨架的反应中,很多情况会发生复杂的付反应,难以高产率地得到希望合成的目标分子。所以,尽可能地减少付反应,而高产率地合成希望得到的杂环化合物成为有机合成化学的重要课题的之—。     

有机锡化合物在有机合成中的应用

讨论了Ｂｕ３ＳｎＨ,Ｂｕ３ＳｎＣｌ,Ｂｕ３ＳｎＬｉ,Ｂｕ３ＳｎＳｉＭｅ３等多种有机锡化合物在有机合成中的应用以及三丁基锡基的各种取代反应,为进一步的研究工作奠定了基础。     

钯催化Suzuki反应的研究进展

钯催化Suzuki偶联反应是有机合成中构建分子中碳-碳键的重要反应之一,由于该反应产物容易分离、催化剂可重复使用等特点,已引起人们的广泛关注.综述了近年来钯催化Su-zuki反应的研究进展,包括Suzuki反应机理、载体催化剂及其在有机合成中的应用等.     

催化剂在有机合成中的应用及发展趋势

随着有机合成理论的日臻完善和绿色化学的日益兴起,催化剂在有机合成中的应用也越来越显得重要。本文就催化剂在有机合成应用中的显著优点作几点介绍,并就催化剂合成的变化趋势做简要的阐述。     

卤代烃在基础有机合成中的应用

卤代烃是有机合成中的重要中间体,借助卤代烃这个中间桥梁可合成很多化合物,研究卤代烃在有机合成中的应用意义重大. 1 卤代烃在有机合成中的应用分析 1.1 烃与烃的衍生物的桥梁 烃类化合物在一定条件下可与卤素单质发生反应生成卤代烃,卤代烃在加热条件下可发生水解反应生成醇,醇氧化可生成醛或酮,醛继续氧化可生成酸,醇和酸发生...     

钯及其配合物催化剂在Heck反应中的应用

钯及其配合物催化剂在有机合成中具有广泛的应用.主要综述钯催化Heck反应近年来的最新进展,重点介绍了各种配体在钯催化Heck反应中的所起的作用.     

二芳基碘鎓盐的应用研究进展

二芳基碘鎓盐是一种用途十分广泛的芳香高价碘(Ⅲ)化合物。在有机合成中二芳基碘鎓盐可以用作许多有机物和无机物,尤其是弱的亲核试剂的芳化试剂;二芳基碘鎓盐与氟-18标记的氟离子的亲核取代反应可用于氟化标记含供电基团芳香化合物,该方法可用于合成正电子发射断层显像技术的显像剂;该化合物还具有显著的光化学活性,可用作阳离子聚合反应的光引发剂。     

光促进温和条件下氯代烷烃与甲酸甲酯的羰基化反应

研究了光促进温和条件下,非贵金属铜化合物、镉化合物催化氯代烷烃与甲酸甲酯的羰基化反应。结果表明,以CuCl_2、CuBr_2或CdI_2为催化剂,可实现氯代烷烃与甲酸甲酯的羰基化反应,得到相应的羧酸甲酯,如以CdI_2为催化剂,氯代环己烷的羰基化产物环己基甲酸甲酯的产率和选择性分别为64%和65%;镉化合物CdCl_2或Cd(OAc)_2单独使用时,无催化活性,向反应体系中加入碘化物,羰基化反应可以顺利进行。MS分析表明I-在镉化合物催化体系中的作用是I-在光照下先原位取代氯代烷烃中的Cl-生成相应的碘代烷烃,然后再与甲酸甲酯进行羰基化反应。     

卡思卡特城堡

It is worthy of noting that, whilst Crookston Castle witnessed the earlier and happier portion of Mary's variegated life,     

不同的吃喝玩乐

一、吃和喝吃苹果 eat an apple, 吃药 take medicine,吃糖 have some sweets,吃饭 have one's meals,吃馆子 dine out,吃惊 be surprised/     

漏洞百出的教育

Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help?     

只要努力,不要后悔

There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love.     

浅谈移民问题

Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject.     

Sister Carrie, an Adherent of Desires

Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities.     

Improvement of one-cycle controller by use of proportional integral differential controller

1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec…     

库克斯顿城堡

城堡, 是欧洲典型的建筑之一, 每个城堡都有一个美丽的传说或是一段历史。从本期开始, 我们将推出“城堡之旅”, 带各位读者去浏览、观赏欧洲各地的城堡, 开始一段文化与历史的旅途!     

The Reader Response Approach to Teaching of English Literature

During interview with English majors, it was found that a majority of students expressed disappointment with their experience of English literature classes. Students' dislike of learning English literature appears to be the major problem of teaching English literature in China. Reader response approach is a good way to solve this problem. In this paper, I explain the rationale behind the reader response approach, such as its origin, definition, features, assumptions, and strategies. Then I illustrate how reader response approach works as a teaching strategy by presenting several teaching models. At last I evaluate its usefuiness for teachers and present the advantages of reader response approach in Chinese context.