取代基对N-H…O=C氢键二聚体中氢键强度的影响

使用MP2方法研究了N-H…O=C氢键二聚体的氢键强度,探讨了不同取代基对N-H…O=C氢键强度的影响.研究发现,可以通过改变取代基的供电性或吸电性来调控氢键强度:乙基等供电子基团对N-H…=C氢键强度的调节作用不大;-NO_2等强吸电子基团可极大地改变N-H…=C氢键强度;质子受体分子中的强吸电子基团如-NO_2可使N-H…O=C氢键强度减弱多达2.6 kcal/mol.自然键轨道(NBO)分析表明,N-H…O=C氢键强度越强,参与形成氢键的氢原子电荷越正,氧原子电荷越负,单体分子间电荷转移越多,N-H…O=C氢键中氧原子孤对电子n(O)对N-H反键轨道σ*(N-H)的二阶稳定化能越大.     

Yb(OTf)3: an efficient catalyst for the synthesis of 3-arylbenzo [f]quinoline-1,2-dicarboxylate derivatives via imino-Diels-Alder reaction

A mild and facile method for the synthesis of 3-arylbenzo[f]quinoline-1,2-dicarboxylate derivatives is reported by an imino-Diels-Alder reaction in high yields (76-92%). This procedure includes a novel three-component reaction of aromatic aldehyde, naphthalen-2-amine, and but-2-ynedioate catalyzed by Yb(OTf)₃ in toluene. The results are obviously different from those of the simple substituted aniline-involved reactions catalyzed by ZnCl₂ or KOH in the literature.     

分级微纳结构MoS_2空心球的制备及其摩擦性能

<正>0引言近年来,具有复杂分级结构的物质由于具有新颖的磁学和电学性能而被广泛用于生物技术[1],催化剂[2],光学器件[3],药物释放[4],光子晶体[5]中。利用各种物理和化学方法,研究者们在制备各种纳米/微米尺度的分级结构上取得了很大的进步,这其中包     

Efficient and direct synthesis of poly-substituted indeno[1,2-b]quinolines assisted by p-toluene sulfonic acid using high-temperature water and microwave heating via one-pot, three-component reaction

Reactions of aldehydes, 1,3-indanedione and enaminones were successfully carried out using p-toluene sulfonic acid (p-TsOH) as a catalyst and high-temperature water as a solvent under microwave irradiation. This method provided several advantages such as rapid reaction times, high yields, and a simple workup procedure. In addition, a possible mechanism to account for the reaction was proposed.     

Synthesis and Crystal Structure of Ethyl2—（2—Amino—3—ethoxycarbonyl—4H—benzopyran—4—yl）cyanoacetate

1 INTRODUCTION Inorganic solid supports as catalysts resulting in higher selectivity, milder conditions and easier work-up have been reported as useful catalysts for many reactions [1~3]. Recently, we have reported the Knoevenagel condensation catalyzed by KF-Al2O3[4]. In this paper, we discussed the crystal structure of the title compound synthesized by the reaction of salicylaldehyde and ethyl cyanoacetate in DMF using the catalyst KF-Al2O3 at room temperature KF-Al2O3. In or…     

7,7-二甲基-2-对溴苯基-4-苯基-5-氧代-1,4,5,6,7,8-六氢化-6H-喹啉的合成及晶体结构

标题化合物C23H22BrNO是由1-(4-溴苯基)-3-苯基-2-丙烯-1-酮与5,5-二甲基-1, 3-环己二酮在N, N-二甲基甲酰胺(DMF)中在NH4OAc催化下反应而得。结构通过单晶X-射线衍射分析确定,其晶体属于单斜晶系,空间群C2/C, a = 19.678(4),b = 13.571(2),c = 17.311(3) 牛琤 = 118.74(1),Mr = 408.33, V = 4055(1) ?,Dc = 1.338 g/cm3, Z = 8, m (MoKa) = 2.038 mm-1, F(000) = 1680, R = 0.0539,wR = 0.1369。X-衍射分析表明,六元环C(10)C(13)C(16)C(17)采用半椅式构象:原子C(10),C(11),C(12),C(16)和C(17)在同一个平面内,而原子C(13)远离平面为0.3282 牛闷矫嬗?个苯环的夹角分别为41.09, 81.97,2个苯环的夹角为75.87。另外在晶体结构中,存在1个分子间氢键。     

稀土硫化物：e–己内酯开环聚合新催化剂

The ring-opening polymerization （ROP） of ε-caprolactone （ε-CL） using lanthanide thiolate complexes [（CH3CsH4）2Sm（μ-SPh）（THF）]2 （1） and Sm（SPh）3（HMPA）3 （2） as initiators has been investigated for the first time. Both of 1 and 2 were found to be highly efficient initiators for the ROP of ε-CL. The poly（ε-caprolactone） （PCL） with molecular weight Mn up to 1.97 ×10^5 and relatively narrow molecular weight distributions （1.20〈MW/Mn〈 2.00） have been obtained in high yield in the temperature range of 35-65℃. According to the polymer yield, 2 showed much higher activity than 1. However, the number-average molecular weight of PCL obtained with 2 was much lower than with 1. The possible polymerization mechanism of the ε-CL polymerization has been proposed based on the results of the end group analysis of the ε-CL oligomer.     

3-取代苄基-6-三氟甲基嘧啶-2,4(1H,3H)-二酮衍生物的合成及其除草活性的研究

为了进一步研究3-取代苄基-6-三氟甲基嘧啶-2,4(1H,3H)-二酮衍生物的除草活性, 以期发现更高活性化合物, 合成了16个未见文献报道的3-取代苄基-6-三氟甲基嘧啶-2,4(1H,3H)-二酮衍生物, 其结构均经过¹H NMR, IR和元素分析确证. 生测结果表明, 嘧啶环1-位取代基的变化, 不仅影响化合物的抑制活性与选择性, 可能还改变了化合物的作用方式. 定量的结构与活性关系研究表明, 当作用对象为油菜时, 化合物的活性可能主要与取代基R的摩尔分子折射常数有关; 当作用对象为稗草时, 化合物的活性可能主要与取代基R的电性参数有关. 1-位为氢时, 有利于对油菜生长的抑制; 1-位为甲基时, 有利于对稗草生长的抑制.     

特殊氢方法预测丙氨酸-α-四肽构象稳定性

使用B3LYP/6-31G*方法优化得到了丙氨酸-α-四肽分子的48个稳定构象.定义了丙氨酸-α-多肽中的特殊氢原子,对构象中与特殊氢原子有关的主要非键相互作用进行分析,提出了使用与特殊氢原子有关的非键相互作用来预测多肽构象的相对稳定性,并将之称为特殊氢方法.基于丙氨酸-α-二肽分子的5个构象和三肽分子的7个构象,确定了特殊氢方法中的与特殊氢原子有关的非键相互作用参数.利用特殊氢方法预测丙氨酸-α-四肽分子的48个构象的相对稳定性,与B3LYP/6-31G*方法的相对能量比较,得到了满意的结果.特殊氢方法得到的相对能量(Y)和B3LYP/6-31G*方法得到的相对能量(X)的线性相关方程为Y=0.9296X 2.2041,相关系数R=0.9532,标准偏差为3.0kJ/mol,偏差绝对值≤4.18kJ/mol的构象占87.5%.