Scheme 1 141
Introduction
The synthesis of nitrogen-containing heterocycles such as
indoles has been one of the most active areas in organic
chemistry due to their extensive existence in a great number
of biologically active compounds.1 Among the numerous
methods for the preparation of these azaheterocycles,2
the intramolecular hydroamination reaction represents a
highly atom-economic way and many kinds of catalysts
have been developed for this transformation.3 Recently, as
a continuation of their pioneering work in zinc-mediated
cyclization of 2-ynylphenol or -aniline, Nakamura and coworkers
have developed a novel tandem cyclization/
nucleophilic addition procedure of N-benzyl-protected
alkynylanilines with electrophiles to form indole derivatives
mediated by one equivalent of n-BuLi, ZnCl2,
[Pd2(dba)3] (cat.) or n-BuLi, ZnCl2, CuCN·2LiCl.4
Our group has demonstrated that the use of alkynyl sulfonamides
bearing a more acidic NH permits the use of diethylzinc
instead of the more basic n-butyllithium.5 The
use of this weaker base allows for the generation of a sufficiently
nucleophilic nitrogen anion for cyclization,
while conceding for a broader functional group tolerance.
Moreover, a catalytic amount of diethylzinc was found to
be able to catalyze the cyclization reaction and when an
excess of diethylzinc was used, the resulting indole zinc
salt intermediate could undergo reactions with acid chloride
or halides to form C2,C3-disubstituted indoles. Notably,
the choice of sulfonyl groups as the protecting group
was crucial to effect such a cyclization process and the use
of unprotected primary amine or acyl-protected substrates
all failed in this transformation.5
Scope and Limitations
Firstly, a series of 4-substituted 2-ethynyl-N-tosylanilines
were prepared and studied in the cyclization reaction with
20 mol% of diethylzinc in toluene (Scheme 1, Table 1). In
general, both the substrates with electron-withdrawing or
electron-donating groups could provide the desired indole
derivative products in excellent yields, while a shorter reaction
time was observed for the electron-withdrawing
ones (Table 1, entries 3–7). It was found that both halogen
and nitro group were well tolerated in the reaction. In addition,
compounds with alkyl and functionalized alkyl
substituents on the acetylene terminal (R1) were also tested
under similar reaction conditions and the corresponding
indole products could also be obtained in high yields
(Table 1, entries 8–11). Unfortunately, when the substituent
was TMS, the cyclization was inhibited completely,
affording only the deprotected aniline 1i after 24 hours
(1l/1i = 6:1) (Table 1, entry 12). 6
翻译一小篇文章(翻译成英文)
The Spring Festival The Spring Festival is the most important festival in China. We have a lot of traditions. First, we clean our houses to sweep away bad luck, and then we paint doors and windows red. It means good luck.The families have a big dinner and we eat jiaozi on...
翻译为1篇作文,英语
Grace:我的笔记本.英语书.数学书在桌字上:My notebook. English books. Mathematics of the word in the table.两张光盘在电脑旁边:2 next to the computer CD-ROM.钥匙在梳装台里:Along with the keys in Taiwan 钢笔在铅笔盒里:Pen in pencil Heli 铅笔盒在地板上:Pencil boxes on the ...
求用英文翻译一段中文
Here is myself introduction: It is very nice to meet you guys, I am a student from NO.1 Jiujiang middle school, grade 2,. This is my first trip to Europe, so i am a little excited.I am a gentle girl and love specially for sweety and milk. Like most common Chinese fa...
求高手英文翻译一封信,要自己翻的!谢谢!
Dear Cousin Frequs,I'm very happy to recieve your letter. We have never met again for 5 years ever since I left Scottland in 1815. I miss our country and the time we grew up together in.I've heard the land you've rented will be taken back soon, and I'm very worried...
那位大哥给翻译一片英文文章
应该说,前面朋友译得可以,但有不少地方错译,理解错误造成专业词汇不到位。我的翻译如下,供你参考:Power station and power plant are both widely used, power station prevailing in many Commonwealth countries and especially in the United Kingdom.当今,广泛使用电站和发电厂,而电站则普遍应用...
英语文章求翻译, 英语大神 快来吧 ,求教~这还不是完整的,加qq4 2...
完整文章,以及翻译如下:The weekends are a time for families in Britain. Often the parents are not at work. Having worked a five-day week from Monday to Friday, Saturdays are a busy time for shops with many families going shopping. Sundays used to be a very special day of ...
求英语文章的翻译。
5. 虽然我们在跳高项目中没有取得好成绩,但我们相信下次会做得更好。6. 我参加了男子400米跑比赛。我全力以赴,成为了第一个冲过终点线的选手。7. TTKis 对我给予了很高的赞扬。这让我更加热爱运动。8. 我梦想成为一名足球运动员。为了实现这个梦想,我每天都会做更多的运动。9. 我希望有朝一...
求1段英文(要求带翻译)
of today joke,the pleasant breeze bright moon of tonight,fine but not the abyss of time,haven't come yet and share the last of wine,but want each rush thing,take good care,friend 今天的欢声笑语,今夜的清风明月,美好却并非永恒,还没来得及分享最后一杯酒,却要各奔东西,珍重,...
求一篇英文翻译(一段2、3分钟的演讲稿)
Dear students, teachers, good afternoon, myname is XX, this time I would like to show you a photograph that I called Jin Feng Shan, I amnot used to do not like to take photos for myself just like some girls do, but whatattract me are scenery, object, or some places ...
一片英语翻译文章
1.The Spring Festival is Chinese New Year. It usually falls in January or February.2.A few days before Spring Festival, people usually do some spring-cleaning. They also buy new clothes for their children.3.On Chinese New Year's Eve, families get together and have a big ...