问题：帮忙翻译段话
类型：求助 (悬赏分:3分)
提问：quick208
等级：▲
版块：有机化学问题(jimuwei,fpcwin1211,netpanda,yjgzfl,Ftian,)
信誉：95%
回复：4
阅读：897
时间：2008-06-29 16:08:54 编辑加入/取消收藏订制/取消短消息举报该贴

The reaction was optimized in several respects. Amount and
granulation of magnesium was found to be important.
Maximum yields were obtained with magnesium turnings (4.5
equiv.). while finer material (e.g. particle size c 0.1 mm) gave
much lower yields. Chemical purity of magnesium also appears to be important. An attempt was made to modify chemically the
surface of magnesium by adding small amounts (0.1-5 mol%) of
various salts: mercury(r1) acetate, mercury(1r) chloride, zinc
chloride, ferric chloride, copper(r1) sulfate and silver(1) acetate.
In all instances, greatly enhanced reactivity was noted, but the
product yieIds were negligible, since hydrogen evolution
become the major reaction. Among solvents tested for the
reaction, were ethanol (96% and abs.), isopropyl alcohol,
formamide and tetrahydrofuran. In tetrahydrofuran the
reductive amination failed to proceed, in formamide it was very
slow and gelatinous, while in alcohols (ethanol, isopropyl)
yields were much lower compared to methanol. Carbonyl
compounds examined in the reaction were aldehydes, ketones,
P-keto esters and y-keto esters, while ammonia (ammonium
acetate), primary and secondary amines were used as an amino
component (see Table 1). Aliphatic ketones reacted with
primary aliphatic amines, a,w-diamines and aromatic amines in
refluxing methanol affording pure secondary amines usually in
good yields (3a-1). Heptan-3-one and pentan-3-one gave lower
yields (ca. 45%) together with l0-15% of unchanged primary
amine, regardless of the amount of magnesium used. In those
instances, an efficient method to remove primary amines in the
presence of secondary ones was developed. After completion of
the reduction, the mixture was treated with 40 mol% of ethyl
formate, thus converting primary amines into the corresponding
formamides. Since secondary amines remain unaffected, they
can be separated as monooxalate salts. Inexpensive and volatile
amines (butylamine, methylamine) were used in excess, in place
of triethylamine. However, all attempts to use secondary
amines in this reaction have failed, since the enamines, slowly
formed in situ, were resistant to reduction. Aromatic ketones
gave complex mixtures with primary amines (TLC and GC)
(3m), while P-keto esters formed stable, conjugated enamines
(3p) and were resistant to reduction. In contrast, the y-keto-
ester, methyl levulinate, underwent smooth reduction followed
by cyclization to furnish the corresponding pyrrolid-2-one (3q).
Primary amines were obtained (3n, 30) albeit in modest yields
(ca. 50%), when ammonium acetate was used in large excess (10
equiv.), in 70% aqueous methanol, together with the
corresponding secondary amines (1 0-20%). When anhydrous
methanol was used, secondary amines become the major
product ( > 50%). Interestingly, the use of ammonium chloride
instead of ammonium acetate, resulted only in hydrogen
evolution, probably due to the greater acidity of ammonium
chloride. Aliphatic aldehydes reacted smoothly with primary
amines at room temperature, to yield the corresponding
secondary amines as a single product (3sv) while at elevated
temperature, side reactions were noted. Aromatic aldehydes,
such as benzaldehyde, gave complex mixtures of products (3r)
similar to aromatic ketones and are not useful substrates in this
reaction.

回复人：david_zhan,★★ () 时间：2008-06-30 21:59:48 编辑

1楼

供参考：
在几个方面对反应进行了优化，发现镁的用量和颗粒大小影响较大。当采用4.5当量的镁时获得了最大产量，而较细的原料（颗粒尺寸在0.1 mm）收率非常低。镁的纯度影响也非常大。尝试过在镁的表面用（0.1-5%mol）的以下各种盐溶液处理：醋酸亚汞，氯化亚汞，氯化锌，氯化铁，硫酸亚铜和醋酸银。在所有的例子中，都大大加强了反应，但是产品产率几乎可以忽略，因为主要是发生了放出氢气的反应。反应的溶剂试验过以下几种：乙醇 (96% 和无水），异丙醇，甲酰胺，四氢呋喃等。四氢呋喃中亚胺的还原不能进行，在甲酰胺中反应非常缓慢并呈凝胶状, 在醇中（乙醇和异丙醇）产率较甲醇中比非常低。试过的羰基化合物包括：醛，酮，P-酮酯和y-酮酯, 当氨(醋酸铵），伯胺和仲胺用于作为胺组分时(见表1），脂肪酮和脂肪伯胺反应，a,w-二胺和芳香胺，在甲醇中回流时仲胺通常获得较好的收率(3a-1)。 3-庚酮和3-戊酮的收率较低（ca. 45%），不管镁的用量是多少，都有 l0-15% 的伯胺没有参加反应。在这些例子里，提出了一种有效的在仲胺存在的情况下除去伯胺的方法。在还原结束后，混合物用40 mol%的甲酸乙酯进行处理，这样可以将伯胺转化为相应的甲酰胺。因为仲胺不发生反应，可以作为单草酸盐进行分离。便宜和易挥发的胺(丁胺，甲胺) 通常过量使用以代替三乙胺。但是，所有尝试使用仲胺的反应都失败了，因为这种条件下缓慢生成的烯胺，对还原有空间阻碍。芳香酮与伯胺反应得到的产物较复杂(TLC 和GC分析) (3m), P-酮酯能生成稳定的共轭的烯胺（3p），还原空间位阻较大。相比较而言，y-酮酯, 戊酮酸甲酯，通过环化得到pyrrolid-2-one (3q)因而还原进行得很顺利。伯胺得到适当的收率(ca. 50%),，当使用大量过量的醋酸铵(10当量)，在70% 的甲醇水溶液中，同时加有10-20%的仲胺，当使用无水甲醇时，仲胺是主要产物( > 50%)。有意思的，用氯化铵替代醋酸铵，仅导致氢气的放出，可能是由于氯化铵的酸性比较强。脂肪醛和伯胺在室温下能顺利地反应，生成相应的仲铵，且产品单一 (3sv) ，但是提高反应温度后，观察到副反应的发生。芳香醛，如苯甲醛得到复杂的混合物(3r) ，与芳香酮类似不能作为这类反应的原料。

回复人：高粱米大碴子,★ () 时间：2008-07-01 07:07:02 编辑	2楼
感觉搂主有点懒！！！！

回复人：klair,▲ (向各位有学识有经验的老师学习！) 时间：2008-07-01 09:24:24 编辑	3楼
这样三番五次地叫人翻译，真有点利用人的感觉。楼主你可以先翻译，然后叫高手指正，这样才有提高啊。

回复人：quick208,▲ (以父之名) 时间：2008-07-01 10:48:02 编辑	4楼
已经打分了！

得分人：david_zhan :3,

问题讨论没有结束...

您尚未进入本论坛,登录之后才可以回贴

7msec