查询词典 disubstituted

According to the helix theory , the algebraic sum value of all rotations of dihedral angle helix is equal to zero in the structure of 1,3-disubstituted cyclohexane derivatives.

按照螺旋理论，1，3-二取代环已烷衍生物的结构中存在的二面角螺旋旋光度代数和为零，不应具有旋光性，但是它们却是光学活性的。

Chapter two 4-Hydroxybenzoic acid is connected with PEG6000 through defoliant DCC at rooom temperature, then the product is refluxed with chloroacetic acid in acetone to afford PEG-bound phenyloxyacetic acid, which is reacted with thionyl chloride, ammonium thiocyanate and arylamines in turn to give PEG-bound disubstituded thioureas. After the cleavage with sodium methoxide in methanol, the eleven disubstituted thioureas are obtained.

第二章 利用PEG6000作载体，通过脱水剂DCC在室温下将对羟基苯甲酸以酯键连接在PEG6000上，再与氯乙酸在较温和的条件下生成PEG6000支载的芳氧乙酸，然后，依次与亚硫酰氯、硫氰酸铵、芳胺反应，生成PEG6000支载的硫脲，最后用甲醇钠的甲醇溶液切割PEG，得到了十一种1，3-二取代硫脲。

We have studied the transition metal complexes catalyzed sequential cross coupling reactions of these new difunctional group reagents with electrophiles and nucleophiles, respectively; developed some convenient and practical new methods for the stereoselective synthesis of disubstituted alkenes, trisubstituted alkenes, conjugated dienes containing heteroatom, conjugated enyne containing heteroatom etc., enriching methodologies for organic synthesis.

继而研究了这些新型双官能试剂在过渡金属配合物催化下分别与亲电试剂、亲核试剂的顺序交叉偶联反应，为双取代烯烃、三取代烯烃、杂原子取代的共轭二烯烃、杂原子取代的共轭烯炔烃等的立体选择合成提供了方便实用的新方法，丰富了烯烃立体选择合成的方法学。

The resting cell of Alcaligenes eutrophus 112R 4 can catalyze the hydrolysis of hydantoin, dihydropyrimidine and succinimide effectively, but not function to 5-monosubstituted hydantoins or 5,5'-disubstituted hydantoins.

该菌能水解海因、二氢尿嘧啶和琥珀酰亚胺，且对琥珀酰亚胺活力最高，但不水解 5 单取代海因和5 ，5' 双取代海因，因而被确定为含有酰亚胺酶。

In the meantime, we proposed a mechanism for this catalytic reaction. According to the possible formation of intermediate B, we designed a disubstituted ketene of more function to re-capture the zwitterion.

在同位素标记基础上，我们推测了这个N-甲基咪唑催化的二组分反应可能的机理，并根据此机理设计用一个二取代的烯酮来捕捉N-甲基咪唑和DMAD形成的两性离子。

A novel zwitterion derived from the addition of thiazole carbene to ketene was discovered and captured by an activated alkyne. In this process, we developed a facile and efficient three-component tandem reaction involving thiazole or benzothiazole carbene, disubstituted ketene and activated alkyne.

我们发现了一种新的噻唑卡宾和烯酮形成的两性离子的存在，并用活泼炔成功捕捉，从而发展了一个新的噻唑卡宾或苯并噻唑卡宾、二取代烯酮和活泼炔的三组分串联反应。

The 1, 3-disubstituted phenylene structure led to bend in the molecular chains of LCP-111 and LCP-116, so that their melting points are lower than that of Xydar, resulting in lower processing temperature and heat resistance.

由于LCP-111和LCP-116的分子链中均引入了间位取代的苯环结构，其分子链发生了弯折，因此它们的熔点均低于全对位结构的Xydar的熔点，但同时也降低了耐热性。

Keywords: disubstituted phosphinosilane;cross coupling reaction; Pd(0)-catalysis; disubstituted phosphine compounds

中文关键词：二取代膦基硅烷；钯(0)-催化反应；交叉偶联反应；二取代膦基化合物

The key problem is to synthesize high stereoselectively trans- 2,5- disubstituted tetrahydrofurans. This thesis sets up a new method to synthesize stereoselectively ?ra玸--2,5-disubstituted tetrahydrofurans by introducing two alkyl groups in 3-C and 5-C of lactol, flash decomposition and hydrogenation.

本文独创新的合成方法：以-乳醇，即-4，10-二氧杂三环[5.2.1.0~(2，6)]-癸-8-烯-3-醇为原料，在其3-位和5-位先反向引入两个取代基，再经过热分解和催化加氢反应，高立体选择性地合成反式-2，5-二取代四氢呋喃。

Among the open-chain crown ethers and cryptands with a same structure, the compounds disubstituted at the amide nitrogen atoms show the larger extractability for Am and Eu than the monosubstituted ones. The compounds disubstituted at the amide nitrogen atoms by two phenyl groups show the larger extractability for Am and Eu than those by two alkyl groups.

3在结构相同的开链冠醚和开链穴醚中，酰胺氮原子上二取代化合物对Am和Eu的萃取能力大于一取代化合物；酰胺氮原子上两个取代基都是苯基的化合物对Am和Eu的萃取能力大于两个取代基都是烷基的化合物。

In the United States, chronic alcoholism and hepatitis C are the most common ones.

在美国，慢性酒精中毒，肝炎是最常见的。

If you have any questions, you can contact me anytime.

如果有任何问题，你可以随时联系我。