新型香豆素类荧光化合物的合成及荧光性质研究

合成了两种香豆素类荧光化合物6,8-二氯-7-羟基香豆素-3-羧酸（DClC）和6-氯-7-羟基香豆素-3-羧酸（MClC）,其中DClC未见文献报道,并通过红外光谱、核磁共振、质谱等手段对产物的结构进行了表征。同时首次研究了这两种香豆素衍生物的紫外、荧光性质,以及不同极性溶剂、pH值、表面活性剂等的影响。结果表明,pH对性质测定影响较大,当pH=10时,DClC和MClC的荧光强度明显增强。     

香豆素-亚胺型Cu~(2+)识别荧光探针的合成及性能

以2,4-二羟基水杨醛为原料经Knoevenagel缩合反应、脱乙酰化反应,再与4-二乙氨基水杨醛经缩合反应,进而通过甲基化合成了新型的香豆素荧光探针.利用核磁共振氢谱(1 H NMR)、碳谱(13 C NMR)和高分辩质谱对所合成的目标化合物进行了结构确认,并测定了其荧光光谱.结果表明,目标化合物对Cu2+有较好的选择性和灵敏度,且当Cu2+浓度在0.66~10μmol·L-1范围内时探针的荧光强度与其浓度有较好的线性关系.Job分析法表明探针与金属离子作用形成1∶1结合的络合物.     

L-7-羟基香豆素氨基酸衍生物的合成及其性能

以保护L-谷氨酸（2）为原料,与N,N′-羰基二咪唑反应制得化合物3; 3与丙二酸单乙酯镁盐反应制得β-酮酯（4）; 4分别与4-氟间苯二酚和4-氯间苯二酚进行Pechmann缩合后,在酸中脱除保护基合成了L-7-羟基香豆素氨基酸（1a）及其两个衍生物（1b, 35.3%和1c, 40.6%）,其结构经¹H NMR, ¹³C NMR和HR-MS(ESI)确证。采用UV-Vis研究了1b和1c的pKa。结果表明：1b和1c的pKa分别为6.21和6.14。两个衍生物的荧光性能与pH密切相关。     

基于ESIPT机理香豆素荧光化合物的合成和光学性质

以3-碘苯酚为原料,经过甲酰化反应、Knoevenagel缩合反应、Sonogashira偶联和还原反应得到以香豆素为母体的目标化合物7-（甲氧基苯乙炔基）香豆素-3-甲醇(5)。化合物5的结构经过¹H NMR, ¹³C NMR和MS(ESI)分析表征确认。并对化合物5的光学性质进行了研究,结果表明：化合物5具有典型的 ESIPT 发光机理,可以构建比率计量型双光子荧光探针。      

吗啉基修饰的新型香豆素Fe~(3+)荧光探针化合物的合成及其性能

间苯二酚与乙酰乙酸乙酯经亲核取代反应制得7-羟基-4-甲基香豆素(1);1与碘甲烷在乙醚中反应制得7-甲氧基-4-甲基香豆素(2);2与N-溴代丁二酰亚胺在四氯化碳中经2步反应制得3-溴-4(溴甲基)-7-甲氧基香豆素(4);4在四氢呋喃溶剂中与吗啉反应合成了一种新型的基于香豆素的荧光探针化合物——3-溴-7-甲氧基-4-(吗啉代)-2H-吡喃-2-酮(5),其结构经~1H NMR,~(13)C NMR和MS表征。光学性能和金属离子识别性能研究结果表明:5的激发波长为340.15 nm,发射波长为408.35 nm;5对Fe~(3+)有良好的识别作用,在1.0×10-5mol·L~(-1)~9.0×10~(-5)mol·L~(-1)可定量检测Fe~(3+)含量。     

香豆素类肼荧光探针的合成及应用

以4-三氟甲基-7-羟基香豆素为荧光母体,4-溴丁酰基为识别基团,合成了一种基于分子内电荷转移机制的肼荧光探针XS-1,其结构经核磁共振氢谱(¹H NMR),核磁共振碳谱(¹³C NMR)和高分辨质谱(HRMS)确证,通过荧光发射光谱研究了探针对肼的响应性能。结果表明,在磷酸盐缓冲液(10 mmol,pH7.4)中,探针XS-1能通过荧光增强作用识别肼,并具有很好的选择性和抗干扰能力,检出限为0.11μmol/L。探针XS-1具有斯托克斯位移大(144 nm)、线性范围宽(0～400μmol/L)、合成简便以及能在水相中检测肼等优点,并已成功用于实际水样中肼的定量检测。     

香豆素席夫碱的Zn~(2+)识别研究

本文采用5-氯水杨醛与3-氨基-7-羟基香豆素反应,合成了一种新型的香豆素席夫碱化合物3-[(5-氯-2-羟基-苯亚甲基)-氨基]-7-羟基香豆素(CHB),并采用核磁共振谱、红外光谱和元素分析对合成产物进行了表征。在CHB的DMF溶液中加入Zn~(2+)后,溶液颜色由无色迅速变为橙黄色,紫外-可见吸收光谱最大吸收峰从380nm红移至480nm,而且该分子探针在580nm处的荧光强度显著增强,可通过肉眼观察到其在365nm紫外灯下发出的荧光,而其它离子加入后荧光变化微弱或没有变化,表明该分子探针对Zn~(2+)的选择性较高。吸收光谱的变化表明CHB与Zn~(2+)形成了新的配合物,采用Benesi-Hilderbrand方程计算出两者之间以1∶1配位。     

新型4-羟基香豆素衍生物的微波合成及其光谱性质

以4-羟基香豆素(a)为原料微波辐射合成了具有独特的生理活性和荧光性能的3,3′,3″,3′″-亚乙四基-4-羟基香豆素(b)、3,3′-苯亚甲基-双-4-羟基香豆素(c)和4-羟基香豆素-1,4-萘醌(d)系列4-羟基香豆素衍生物, 采用元素分析、红外光谱、核磁共振及质谱表征了产物的结构, 并对其紫外-可见吸收光谱及荧光光谱性质进行了研究, 探索了化合物的微观结构与其光学性能之间的关系. 研究结果表明, 具有“近平面”、大π共轭和对称型结构的化合物b具有较大的摩尔吸光系数及强荧光特性, 且浓度在0.50~1.50×10^-4 mol/L范围时, 其荧光强度随着浓度的降低而呈线性增加; 在pH=1.81~6.09时, 荧光强度随pH降低而减弱, 在pH 8.36~11.98时, 荧光强度随pH升高而减弱. 此外, 牛血清白蛋白(BSA)及脱氧核糖核酸(DNA)可与该化合物发生相互作用, 进而敏化增强该分子的内源荧光.     

基于苯乙烯吡啶衍生物pH荧光探针的研究与应用

本文以苯乙烯基吡啶衍生物为荧光团,酚羟基为脱质子基团,设计并合成了一种具有双重功能的可视化pH值荧光探针。探针表现出强烈的pH依赖性,且伴有溶液颜色的显著变化。此外,探针还显示出良好的光稳定性和抗金属离子干扰能力。pH滴定实验表明该探针的荧光强度在pH 6.00至8.85之间随pH值增大而降低,且线性关系良好。探针的pKa值为7.21,对于细胞内pH值的研究是有价值的。该探针可广泛用于检测和定量测定生物系统中轻微的pH变化。     

基于香豆素荧光团的高选择性Fe~(3+)荧光分子探针研究

设计合成了四种含有酰胺和酯基结构的香豆素荧光分子探针,其结构通过1H NMR、13C NMR和HRMS进行了表征,并对探针进行了常见金属离子识别性能的研究。发现该类探针对Fe3+产生荧光淬灭性响应,其中7-位带有二乙氨基的2-(7-二乙氨基香豆素-3-甲酰胺基)乙酸乙酯(C3)和3-(7-二乙氨基香豆素-3-甲酰胺基)乙酸丙酯(C4)对Fe3+的淬灭比例达到99.5%和99.6%,可作为识别Fe3+的探针。     

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.