基于C=N双键异构化传感机制的荧光探针

多种传感机制已经被用于荧光探针分子的设计中,其中,基于C=N双键异构化传感机制的荧光探针的研究近年来引起了较大关注。本文归纳总结了过去10年基于C=N双键异构化传感机制的阳离子、阴离子和中性分子探针的发展情况。文章最后对其应用前景及发展趋势进行了展望。     

C＝N双键的不对称烯丙基化反应

详细地综述了有关C＝N双键立体选择性烯丙基化反应的研究进展. 重点讲述了使用手性辅助基团、手性试剂以及不对称催化剂进行C＝N双键不对称烯丙基化的方法.     

选择性合成(1,3-二苯基-2-亚丁烯基)二苯甲胺席夫碱及其光催化选择性双键转移的研究

席夫碱是一类具有多功能结构的化合物.本文使用二苯甲胺和苯乙酮为原料合成了(1,3-二苯基-2-亚丁烯基)二苯甲胺席夫碱,并进行了光催化选择性双键转移的研究.结果 表明,当苯乙酮与二苯甲胺投料比为3∶1,先在135C反应4h,然后升温到165C继续反应3h,可选择性合成(1,3-二苯基-2-亚丁烯基)二苯甲胺席夫碱.该席...     

溴与不同取代C=C双键反应的机理和立体选择性

溴与C=C双键的反应是有机化学中一类常见的基元反应。溴与烯烃的C=C双键发生亲电加成反应,脂肪烯烃经过三元环正离子中间体再亲核开环机理,形成立体专一的反式加成产物;而芳基烯烃形成的三元环中间体,由于芳基对碳正离子的稳定作用,其苯甲位C―Br键容易断裂,会得到顺式和反式加成产物的混合物。溴与酮和酰氯形成的烯醇或烯醇负离子发生亲电取代,反应中溴不会与其C=C双键形成三元环正离子中间体。类似地,溴与烯醇醚和烯胺的反应也不经过三元环正离子中间体,分别生成非立体专一的加成和取代产物。本文通过参与该步基元反应的分子轨道合理地解释了溴与这两类底物反应的机理和立体选择性的区别,并总结了溴与不同C=C双键反应机理的判断方法,便于教师讲授和学生理解。     

N,N-二烯丙基甲基胺的相转移催化合成

相转移催化剂;聚乙二醇-400;N;N-二烯丙基甲基胺的相转移催化合成     

芳胺常压气相N－烷基化反应研究

在固定床催化反应器中常压下研究了芳胺和醇的气相法Ｎ－烷基化反应。考察了γ－Ａｌ２Ｏ３系列催化剂的反应性能，筛选出了两种适用于苯胺Ｎ－甲基化反应且性能较好的催化剂。反应条件为：在甲醇和苯胺的摩尔比为３１时，反应温度为２８０℃，液时空速为０．３ｈ－１的条件下，苯胺转化率为９９％，生成Ｎ，Ｎ－二甲基苯胺（ＤＭＡ）的选择性为９２％。研究了甲醇和芳环上不同位置取代的甲基苯胺的反应规律，其转化率顺序：苯胺≈对一甲苯胺≈间－甲苯胺＞邻－甲苯胺。从Ｃ１到Ｃ４不同结构的醇和苯胺反应的规律研究，证明随醇中碳原子数目的增加，醇的反应活性降低，正构醇和苯胺反应和异构醇与苯胺反应随温度升高的变化趋势相反。     

光照下钴镍盐催化肉桂醛的转移加氢反应

以甲醇为氢源,研究了光照下金属镍盐、钴盐催化肉桂醛的转移加氢反应.结果表明,以Co(OAc)2和Ni(OAc)2为催化剂,肉桂醛可以发生催化转移加氢反应,得到肉桂醇;就催化剂的转移加氢活性和产物肉桂醇的选择性而言,Co(OAc)2的催化效果更好.与此同时,在反应体系中添加NaOAc和Na2C2O4等碱性添加剂可提高肉桂...     

液—液相转移催化法合成芳氧基乙酰芳胺

N-(二芳基醚)酰胺和N-(2-噻唑基)芳氧基乙酰胺类化合物可用作除草剂,它们的经典合成方法由酰氧和胺在化学计算量的缚酸剂吡啶或三乙胺的存在下制得。亦可不加缚酸剂使羧酸与三氯化磷作用生成酰氯的同时紧接着与胺反应而合成。两种方法的产率都低,后一方法的反应条件还比较苛刻。     

自由基C69N及双体(C69N)2结构和电子光谱的理论研究

用INDO系列方法对自由基C₆₉N(Cs)及双体(C₆₉N)₂(C₂h)进行了理论研究,结果表明:笼骨架上N的掺入使C₇₀笼发生畸变,N向笼外突出,与氮相连的碳(6-6环上的C)自旋密度较大,2个C₆₉N自由基在这个碳上以C-C单键连接,形成双体为C₂h对称性,N与附近的3个碳均以单键连接,并不断开。理论计算的电子光谱与实验吻合较好,(C₆₉N)₂易分解为单体C₆₉N.     

光照下非贵金属催化的1-辛烯转移加氢反应

光照下,以甲醇为氢源,以NiCl_2、Ni(OAc)_2或CoCl_2为催化剂,1-辛烯可以发生催化转移加氢反应,得到辛烷,主要副产物为双键异构的2-辛烯和3-辛烯.综合催化剂的加氢活性和产物辛烷的选择性,NiCl_2的催化效果最好,且NiCl_2的催化活性在293～333K范围内随温度升高而增加.以NiCl_2为催化剂,在反应体系中添加三正丁胺,于293K下反应24h,辛烷的产率由45%提高到65%,选择性由57%提高到70%.     

The N and C solid state NMR study of intramolecular hydrogen bond in some Schiff bases

In present work set of eight Schiff bases derived from substituted salicylaldehydes and aliphatic and aromatic amines has been studied in the solid state by ¹⁵N and ¹³C CPMAS NMR methods. ¹⁵N CPMAS NMR measurement is especially useful for investigation of the tautomerism in the compounds considered, owing to the large difference in the nitrogen chemical shifts of OH and NH tautomers. In the solid state, four of the compounds examined were shown by ¹⁵N CPMAS NMR to exist as OH tautomeric forms, and the remaining four as the corresponding NH forms with different stage of proton transfer process, from oxygen to nitrogen site.

This was confirmed by ¹³C CPMAS. The results reported were compared with those obtained for only two compounds in CDCl₃ solutions (solubility problems).     

C=C Bond Oxidative Cleavage of BODIPY Photocages by Visible Light

Photocages for protection and the controlled release of bioactive compounds have been widely investigated. However, the vast majority of these photocages employ the cleavage of single bonds and high-energy ultraviolet light. The construction of a photoactivation system that uses visible light to cleave unsaturated bonds still remains a challenge. Herein, we report a regioselective oxidative cleavage of C=C bonds from a boron-dipyrrolemethene (BODIPY)-based photocage by illumination at 630 nm, resulting in a free aldehyde and a thiol fluorescent probe. This strategy was demonstrated in live HeLa cells, and the generated α-formyl-BODIPY allowed real-time monitoring of aldehyde release in the cells. In particular, it is shown that a mannose-functionalized photocage can target HepG2 cells.     

Intramolecular Nitrene Insertion into Saturated C−H-Bond-Mediated C−N Bond Cleavage of a Coordinated NHC Ligand

Ruthenium(II) complexes bearing a tridentate bis(N-heterocyclic carbene) ligand reacted with iminoiodanes (PhI=NR) resulting in the formation of isolable ruthenium(III)–amido intermediates, which underwent cleavage of a C−N bond of the tridentate ligand and formation of an N-substituted imine group. The Ru^III–amido intermediates have been characterized by ¹H NMR, UV/Vis, ESI-MS, and X-ray crystallography. DFT calculations were performed to provide insight into the reaction mechanism.     

C59XH（X=N,B）与1,3-丁二烯Diels-Alder环加成反应的区域选择性

应用半经验的AMI和密度泛函B3LYP/6-31G*方法对1,3-丁二烯与C59XH(X=N,B)Diels-Alder环加成反应的区域选择性进行理论研究,选择一些有代表性的C59XH(X=N,B)的6-16键探讨环加成反应的机理.1,3-丁二烯与C59NH进行的Diels-Alder反应,随着加成位置远离C59NH的N原子,活化能越来越低,但都比1,3-丁二烯与C60相应反应的活化能高.与此相反,对于1,3-丁二烯与C59BH进行的环加成反应.加成位置最靠近B原子的2,12/r-和2,12/f-过渡态的势垒最低,并且比1,3-丁二烯与C60进行环加成反应的活化能约低18 kJ·mol-1,其产物也是热力学最稳定的.与C60相应的反应相比,C59NH和C59BH中N和B原子不同的电子性质对其邻位双键进行Diels-Alder环加成反应的活性产生了不同影响,前者使反应活性降低,后者使反应活性增强.     

Palladium‐catalyzed unstrained C(sp3)―N bond activation: the synthesis of N,N‐dimethylacetamide by carbonylation of trimethylamine

This work describes a highly efficient unstrained C(sp³)―N bond activation approach for synthesis of N,N‐dimethylacetamide (DMAc) via catalytic carbonylation of trimethylamine using a PdCl₂/bipy (bipy = 2,2′‐bipyridine)/Me₄NI catalyst system. A low Pd catalyst dosage (1.0 mol%) is sufficient for high selectivity (98.1%) and yield (90.8%), with a turnover number (TON) of 90.0 mmol of DMAc obtained per mmol of PdCl₂ employed under mild reaction conditions. The influence of reaction parameters such as catalyst precursor dosage, ligand type and promoter on activity is investigated. This work also discusses in detail the halide promoter's role in the reaction, and provides a plausible mechanism based on the intermediates methyl iodide and acetyl iodide. Analyses indicate that the carbonylation of trimethylamine may proceed through an active intermediate acetyl iodide formed by carbonylation of methyl iodide generated from the decomposition of the promoter Me₄NI under reaction conditions. The formation of acetyl iodide favors the cleaving efficiency of the inert unstrained C(sp³)―N bond of trimethylamine. Copyright © 2013 John Wiley & Sons, Ltd.     

Studies on cyanosilylation reaction catalyzed by Ln?N complexes

A novel family of Ln? N complexes was synthesized by two methods and as the Lewis acidic catalysts in application to the cyanosilylation of prochiral ketones and aldehydes, which gave yields > 99% of some cyano trimethylsilyl ethers from the wide range of aldehyde substrates and moderate yields from the ketone substrates at room temperature using 20 mol% catalyst loadings. Copyright © 2008 John Wiley & Sons, Ltd.     

Crystal structure of Schiff base derivative of gossypol with 3,6,9-trioxa-decylamine

Crystals of the Schiff base derivative of gossypol with 3,6,9-trioxa-decylamine were examined using X-ray diffraction, FT-IR and CPMAS spectroscopy. The Schiff base crystallizes as a racemate in the space group C2/c with a=24.390(5), b=12.026(2), c=14.810(3) Å, β=102.78(3)°, and Z=4. The results of the FT-IR, and CPMAS study of the crystals are in agreement with the X-ray data. The FT-IR spectrum of the crystals shows that the OH groups at position 1,1′ and 6,6′ as well as the N₁₆-H proton are involved in weak intermolecular and intramolecular hydrogen bonds, respectively. The FTIR and CP-MAS spectral behaviour is in agreement with the crystallographic results demonstrating the existence of the enamine-enamine tautomeric form of the Schiff base studied.     

Activation of – N=CH – bond in a Schiff base by divalent nickel monitored by NMR evidence

The Schiff base, 2–salicylidene–4–aminophenyl benzimidazole in ethanol undergoes activation of –N=CH– bond by Ni²⁺ in the presence of ammonia or primary alkyl amine to produce nickel complexes of the formula Ni{o–C₆H₄(O)CH NR}₂ . n H₂O [R = H, Me; n = 0; R = Et, n = 0.5] and 4–aminophenyl benzimidazole. The products have been identified by elemental analysis, magnetic susceptibility measurements and IR, ESR, mass and extensive NMR spectral studies. The possible mechanism for the activation of –N=CH – bond has also been proposed. Copyright © 2012 John Wiley & Sons, Ltd.