3-氰基-1,4-二氢吡啶衍生物的合成

1,4-二氢吡啶类化合物具有多种生物活性,在临床上受到广泛应用,普遍用于各类心脑血管疾病的治疗。以3-氰基吡啶和含不同取代基的溴化苄为原料在加热回流15h的条件下合成中间体盐;以硼氢化钾(KBH_4)作为还原剂,在冰水浴搅拌的情况下,与中间体盐反应,合成了15个结构新颖的1,4-二氢吡啶衍生物(a～o),产率可达85%～90%,其结构经~1H NMR、~(13)C NMR和质谱进行表征。该方法具有成本低、环境友好、操作简单、产率高的特点。     

1,4-二氢吡啶衍生物合成方法的改进和芳构化研究

改进了Hantzsch合成法,通过一锅煮合成1,4-二氢吡啶衍生物,大大缩短了反应时间,操作简便,发现氯化铁是一个较好的1,4-二氢吡啶衍生物芳构化的氧化剂。     

1,4-二氢吡啶衍生物合成方法的改进和芳构化研究

改进了Hantzsch合成法,通过一锅煮合成1,4-二氢吡啶衍生物,大大缩短了反应时间,操作简便,发现氯化铁是一个较好的1,4-二氢吡啶衍生物芳构化的氧化剂。     

单取代苯乙醛及其二氢吡啶衍生物的合成

以单取代苯乙酸为原料,在SOCl2/MeOH中制得甲酯;用NaBH4/MeOH将其还原制得取代苯乙醇;再用戴斯-马丁氧化剂氧化制得单取代苯乙醛;最后通过Hantzsch反应合成了9个1,4-二氢吡啶衍生物——2,6-二甲基-3,5-二乙氧羰基-4-取代苄基-1,4-二氢吡啶(4a～4i),其结构经1H NMR,13C NMR和MS表征,其中4b～4i为新化合物。     

杯[6]-1,4-冠-4四酰胺基硫脲衍生物的合成

对叔丁基杯[6]-1,4-冠-4在NaH/二氧六环中与溴乙酸乙酯反应生成对叔丁基杯[6]-1,4-冠-4四乙酸乙酯衍生物(2);2与水合肼反应得对叔丁基杯[6]-1,4-冠-4四酰肼衍生物(3);3与异硫氰酸苯酯反应合成了对叔丁基杯[6]-1,4-冠-4四酰胺基硫脲衍生物(4). 2～4为新化合物,其结构经1H NMR, IR, ESI-MS和元素分析表征.     

水介质中双(1,4-二氢吡啶)衍生物的合成

水介质中在苄基三乙基氯化铵(TEBAC)催化下,利用对苯二甲醛与1,3-二羰基化合物及醋酸铵的多组分反应合成了一系列官能团化双(1,4-二氢吡啶)衍生物。产物的结构通过红外光谱和核磁共振氢谱确定.该方法具有操作简单、产率高、环境友好等特点,为新型1,4-二氢吡啶衍生物的合成提供了一条绿色合成的途径。     

噻吩甲酰硫脲衍生物的合成及其抑菌活性

通过3-巯基-2-丁酮与取代硅基丙炔酸甲酯的环合、酯的选择性水解、异硫氰化、胺化等步骤合成了13个未见报道的噻吩甲酰硫脲衍生物.各噻吩甲酰硫脲衍生物的结构经~1H NMR、~(13)C NMR和元素分析的确证,其对小麦全蚀病、水稻纹枯病病原菌的抑菌活性经平皿法进行了测试.结果表明,大部分噻吩甲酰硫脲衍生物对小麦全蚀病病原菌具有一定抑制活性,其中1-环丙基-3-(4,5-二甲基噻吩-3-甲酰基)硫脲(8c)抑菌活性表现较为突出,在10 mg/L浓度下其抑菌活性接近对照硅噻菌胺的水平.结构分析表明噻吩-3-甲酰硫脲衍生物噻吩环2位官能团的大小对小麦全蚀病菌抑制活性的影响不明显.     

具有生物活性的1,4-二氢吡啶衍生物的水热法合成及结构表征

1,4-二氢吡啶衍生物具有很好的生理活性。在医学上用作心血管疾病的防治保健药物,不仅能治疗肠胃疾病、雷诺氏病、脂肪肝、中毒性肝炎,也有抗衰老、防早熟等作用,还可以用作治疗肺动脉高压和癫痫病的辅助药物[1-2]。近年又发现1,4-二氢吡啶衍生物不但是一类高效的钙拮抗剂,亦是一种绿色饲料添加剂。它的合成通常采用文献报道的Hantzsch法合成[3],即将干燥氨气通入乙酰乙酸乙酯与醛的混合溶液中。该反应时间长、操作复杂,且氨气易对环境造成污染。正因为此,越来越多的化学家和药物学家将有机合成的研究重点放在对环境无污染的绿色合成上。如…     

C2轴手性硫脲的合成及其微波辅助下催化Biginelli反应性能

本文合成了三种具有轴手性联芳基骨架的多手性中心、多氢键的结构对称型多活性中心硫脲催化剂,并将其应用于催化Biginelli反应合成3,4-二氢嘧啶硫酮。结果表明,所合成的新型轴手性硫脲均表现出良好的催化作用,能有效地提高Biginelli反应的收率和对映选择性。     

2,5-二取代噻吩衍生物的“一锅化”串联合成及光学性质

以芳基乙炔与硫脲为起始原料,通过一锅法,经过在无溶剂条件下的氧化偶联反应和在水相中的成环反应,两步串联绿色合成了2,5-二苯基噻吩及其衍生物.所合成化合物经~1H NMR,~(13)C NMR,HRMS表征,均为目标产物.在此基础上,进一步探索了所合成化合物的UV和荧光性质,实验结果表明,所合成化合物的紫外最大吸收波长在292~341 nm之间,荧光光谱表明该类化合物具有良好的荧光性,在甲醇中最大发射波长在386~454.5 nm之间,在二氯甲烷中测定的最大发射波长在390~412 nm之间.实验结果显示,随共轭体系增大,荧光发射波长发生红移.     

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.