无催化剂、无溶剂条件下合成螺氧化吲哚衍生物

报道了在无催化剂、无溶剂条件下,靛红、丙二腈和1,3-二羰基化合物在80℃反应温度下,通过"一锅煮"三组分反应合成了螺氧化吲哚衍生物-该法具有反应条件温和、操作简单、产率较高和对环境友好等优点.     

含哒嗪酮的肟醚类化合物的合成

4, 5-二氯哒嗪酮4与肟在NaH/DMF或者NaOH/acetone的条件下反应, 合成了含哒嗪酮的肟醚类化合物1a-f。4-氯-5(β-溴乙氧基)哒嗪酮3在相转移催化的条件下, 与芳香醛(酮)肟反应得到单一的产物2, 但是和脂肪酮肟反应则生成1和2的混合物。文中讨论了不同亲核试剂及反应条件下对该反应及其区域选择性的影响。     

1-苯基-3-甲基-4-苯甲酰基吡唑啉酮/PdCl2在温和条件下催化Suzuki偶联反应的研究

考察了商品化的简单非膦配体1-苯基-3-甲基-4-苯甲酰基吡唑啉酮在有氧温和条件下的Suzuki偶联反应活性,探讨了反应温度、反应时间、溶剂以及碱对反应的影响。结果表明,该配体在优化的反应条件下能高效催化不同溴代反应物和氯代反应物与苯硼酸的交叉偶联反应;提高反应温度、延长反应时间和引入质子性极性有机/水混合溶剂有利于偶联反应的进行。     

1,2,4-三苯基环戊二烯的合成及其烷基化反应

测定了颇哪醇在酸性条件下所得的脱水产物的分子结构.结果表明,在酸性条件下颇哪醇的脱水反应优于重排反应,由此合成了1,2,4-三苯基环戊二烯.该环戊二烯衍生物的烷基化反应,在通常条件下优先发生在碳环的第5位碳原子上,但在苛刻的剧烈反应条件下,进而发生在碳环的第3位碳原子上.讨论了脱水反应和烷基化反应的机理.     

超声催化α-酮酰胺的Henry反应研究

三乙胺催化α-酮酰胺与硝基甲烷的Henry反应,在传统条件下该反应需要12～120 h;在超声(100 W)催化下,条件温和,反应速度快,产率提高,反应50 min得到90%的产率。研究表明超声波技术可以加速Henry反应。     

微波辐射下离子液体介质中经由Passerini反应合成α-酰氧基酰胺及α-酰氧基酰胺-嘧啶核苷杂化体

研究了微波辐射下离子液体介质中的羧酸、醛及异腈的三组分反应,即Passerini反应.研究发现,该反应可在微波辐射条件下很快完成,并以较高的收率生成相应的α-酰氧基酰胺类衍生物.与文献方法相比,该方法具有对环境友好、效率高、操作简便、反应条件温和等优点.笔者已经成功地将这一方法应用到了具有潜在生物活性的α-酰氧基酰胺-...     

微波辐射固相合成4-三氟甲基-7-羟基-6-氯香豆素

分别以无水氯化锌、对甲苯磺酸为催化剂,采用微波辐射法,在无溶剂条件下由4-氯间苯二酚与三氟乙酰乙酸乙酯缩合制备标题化合物;优化了反应条件.结果表明,在微波辐射下,无水氯化锌对该反应有较好的催化活性,相应的4-三氟甲基-7-羟基-6-氯香豆素的产率可达73.0%.优化的反应条件为:4-氯间苯二酚、三氟乙酰乙酸乙酯和无水ZnCl2的摩尔比为1∶1.1∶0.9,微波辐射功率800W,辐射时间20min,反应温度85℃.     

光照条件下碳-硅键断裂及其溴代反应研究

研究了在高能量紫外光照条件下,苄基硅试剂的碳-硅键断裂过程及随后的高效溴代反应.该反应在紫外光照条件下,室温下即可温和且高效地进行,从而发展了一套新型的由苄基硅试剂合成苄基溴代物的方法.同时提出了该反应的可能机理.     

机械研磨法合成5-(2-硝基烷基)米氏酸衍生物

以5-亚烃基米氏酸衍生物与硝基烷烃类化合物在固相机械研磨条件下,在碱存在下,反应合成5-(2-硝基烷基)米氏酸衍生物,探讨了碱、反应物料比等条件对产物产率的影响,优化反应条件为:等物质的量的甲醇钠,反应温度50℃,反应时间30 min.该方法适用于合成多种5-(2-硝基烷基)米氏酸衍生物,为γ-氨基丁酸衍生物的合成提供...     

1-(5-二茂铁基-1,3,4-噻二唑-2-基)哌啶-2-酮的合成及表征

本文报道1-(5-二茂铁基-1,3,4-噻二唑-2-基)哌啶-2-酮(1)的合成。首先,在乙酸催化下,二茂铁甲醛(2)和氨基硫脲(3)反应得到二茂铁亚胺基硫脲衍生物(4)。然后,在三氯化铁作用下,中间体4发生关环反应得到5-二茂铁基-1,3,4-噻二唑-2-胺(5)。中间体5再与5-溴戊酰氯(6)发生N-酰基化反应得到5-溴-N-(5-二茂铁基-1,3,4-噻二唑-2-基)戊酰胺(7)。最后,在碱性条件下,中间体7发生分子内关环反应得到目标化合物(1)。中间体及产物结构经¹H NMR、¹³C NMR和ESI-MS表征,产物1结构进一步通过X-单晶衍射确证。然后分别考察了中间体5及产物1收率的主要影响因素,确定中间体5合成的适宜条件为：三氯化铁的用量为n(三氯化铁)∶n(中间体4)=4∶1,反应温度80℃,反应时间为15 h,在该条件下,中间体5的收率达到61.9%;确定产物1合成的适宜条件为：反应溶剂为二氧六环,物料比为n(DIEA)∶n(6)∶(5)=3.0∶1.2∶1.0、反应温度为80℃,反应时间为4 h,在该条件下,产物1收率达到68...     

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.     

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.     

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.