分子间作用力对咪唑盐介晶相性质的影响

通过对咪唑环1位(N1)取代烷基、3位(N3)取代基及阴离子的修饰合成了一系列具有近晶A (SmA)相的咪唑类离子液晶. 利用差示扫描量热法、单晶衍射、小角度X射线衍射等手段研究了咪唑盐的介晶相温度范围、介晶态的结构, 并测量了部分咪唑盐的各向异性导电率. 结果表明, 咪唑环N1取代烷基、N3取代基及咪唑盐的阴离子会改变分子间范德华力和氢键, 从而对咪唑盐的介晶相性质产生影响. 此外, 当乙烯基引入到咪唑环N3位置时, 咪唑盐相邻的层结构之间形成π-π堆积作用, 不仅有利于介晶态的形成, 同时使氟硼酸类离子液晶具有最大的层间距和最小的各向异性导电率. 这一结果表明, 调控离子液晶的性质时必须综合考虑各种分子间作用力的影响.     

1-烷基-3-甲基咪唑溴化盐离子液体的晶体结构及性能

以不同链长溴代烷烃和N-甲基咪唑反应得到1-烷基-3-甲基咪唑溴化盐,用元素分析和核磁共振对化合物进行了表征.室温下用溶剂蒸发法得到了单晶,并用X射线单晶衍射法测定了晶体结构,该晶体属于三斜晶系,空间群为P-1.化合物采用双分子层结构,水分子参与结构的形成,整个化合物由交叉的线性烷基链、咪唑头基、溴离子和水分子组成,溴离子和水分子之间较强的氢键作用在(010)方向上形成了一个无限的O-H···Br氢键链.用偏光显微镜、差示扫描量热(DSC)技术研究了其液晶行为,证明其一水合物为近晶相热致液晶.液晶区域的温度范围较宽说明水分子起到稳定作用.     

新型氮二烷基吗啉盐酸盐离子液体的合成及其性能研究

以N-甲基吗啉和N-乙基吗啉为原料合成了系列新型的氮二烷基吗啉季铵盐类离子液体, 所有新化合物经元素分析、1H NMR确认了其结构, 同时测定了该类化合物的热稳定性、电导率以及对聚丙烯腈的溶解能力. 试验结果表明, 大多数化合物的熔点较低, 为室温离子液体. 该类化合物具有较好的热稳定性, 可应用于电极和表面活性剂领域. 且N-甲基-N-丁基吗啉盐酸盐具备对聚丙烯腈的溶解能力.     

室温离子液体在过渡金属催化反应中的应用研究进展

室温离子液体(RTILs)是在室温或近于室温下呈液态的由离子构成的盐类．如图1所示，RTILs按阳离子类型可以分为4类：烷基季铵盐离子；烷基季鳞盐离子；N，N-二烷基咪唑离子和N-烷基吡啶离子．按阴离子可分为：氯化盐 AlX3(X=卤素)和含有RF1^-,PF6^-等阴离子的离子液体．     

酸性离子液体的合成和光谱表征

合成了基于N-甲基咪唑、2-吡咯烷酮阳离子的两个Br nsted酸性离子液体系列:[Hmim]HSO4/BF4、[Hnhp]HSO4/BF4以及两种—SO3H功能化酸性离子液体1-(3-磺酸基)丙基-3-甲基咪唑硫酸氢盐([C3SO3Hmim]HSO4)、N-(3-磺酸基)丙基吡咯烷酮硫酸氢盐([C4SO4Hnnp]HSO4)。其中,[Hnhp]HSO4/BF4,[C4SO4Hnnp]HSO4是本实验设计合成的新型酸性离子液体,而咪唑类离子液体用于对照。上述6种离子液体均以核磁共振、电喷雾质谱、红外光谱和紫外光谱分析法对结构加以表征并确认;并以它们作为溶剂和催化剂对乙酸、乙醇酯化反应进行初步试验,结果表明所合成的新型酸性离子液体(尤其是引入磺酸基的)是酯化反应较理想的绿色液体酸催化剂。     

手性胶束中的不对称Micheal反主尖

本文研究了手性表面活性剂N,N-二甲基-N-十二烷基麻黄素溴化铵及N,N-二甲基-N-十六烷基麻黄素溴化铵所形成的手性胶束体系中,以六氢吡啶作为碱催化剂,硝基甲烷或硫酚对查耳酮类化合物的Michael加成反应.     

离子液热条件下金属有机骨架化合物的合成

以1-丁基-3-甲基咪唑氟硼酸盐为溶剂, 在离子液热条件下得到两个化合物Zn3(BDC)3(MIA)2(1) 和Zn(HBTZ)(MIA)(BPY)(2). X射线衍射分析表明, 两种化合物的晶体分别属于单斜晶系, C2/c空间群和正交晶系, Fdd2空间群. 化合物1为三维结构, 在除去端基的N-甲基咪唑后, 形成了大约0.9 nm×0.9 nm的一维菱形孔道. 化合物2中的链状次级结构单元则通过π键和氢键作用形成了超分子结构.     

手性胶束中的有机反应(Ⅴ)——手性胶束中查耳酮的不对称环氧化

本文报道查耳酮用H₂O₂在手性表面活性剂N,N-二甲基-N-十二烷基麻黄素澳化铵(1a)及N,N-二甲基-N-十六烷基麻黄素溴化铵(1b)形成的手性胶柬水溶液中的不对称环氧化反应,得到相应的手性α,β-环氧酮,对映体过量为5～8%.     

负载型二乙酰氧碘苯与功能离子液体协同氧化醇为醛酮

将聚苯乙烯树脂(PS)先碘化再乙酰基化,制得了负载型二乙酰氧碘苯(PS-DIB)作为氧化剂。2,2,6,6-四甲基-N-氧自由基哌啶醇(TeMPO)与1,4-二溴丁烷反应生成4-溴丁氧基-2,2,6,6-四甲基-哌啶-1-氧化物,再与N-甲基咪唑发生季铵化反应,生成的溴化季铵盐与四氟硼酸钠进行离子交换制得氟硼酸型2,2,6,6-四甲基-N-氧自由基哌啶负载离子液体(TeMPO-IL)。室温下,以离子液体1-甲基-3-丁基咪唑四氟硼酸盐([bmim]BF4)为溶剂,PS-DIB为氧化剂,TeMPO-IL为催化剂,选择性协同氧化各种醇为相应的醛或酮。在实验条件范围内未检测到羧酸副产物。氧化剂、催化剂和溶剂均可循环使用,在苯甲醇的氧化中,循环使用5次,反应的转化率和收率均保持基本不变。     

N-烷基吩噻嗪化合物与四氯化碳的光诱导电子转移反应

N-烷基吩噻嗪化合物(1a～1c)与四氯化碳之间的光诱导电子转移反应生成3-(N′-吩噻嗪基羰基)-N-烷基吩噻嗪(2a, 2b),3-(N′-烷基吩噻嗪基-3′-羰基)-N-烷基吩噻嗪(3b, 3c), 及N-烷基吩噻嗪正离子自由基的四氯化碳盐1+.CCl-.C4 (4a～4c),提出了光诱导电子转移机理.     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd₂(dba)₃-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring.     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Synthesis of substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles by intramolecular nitrilimine cycloaddition

Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.