Chromeno[2,3-c]pyrroles by one-pot multicomponent domino addition–amination reaction

A new aspect concerning chromone chemistry leading to the one-pot synthesis of chromeno[2,3-c]pyrroles is described. The synthesis involves a multicomponent reaction of 3-formylchromones with isocyanides and azodicarboxylates, whereupon novel chromeno[2,3-c]pyrrole derivatives were formed in good yields. The structures of the products were elucidated by 1D and 2D NMR experiments and were unambiguously confirmed by the use of crystal X-ray diffraction analysis. Full assignment of all ¹H and ¹³C NMR chemical shifts has been achieved. A plausible mechanistic scheme is proposed.     

Diastereoselective one-pot synthesis of novel ABCD-fused chromeno[2,3-d]pyrazolo[3,4-b]pyridines

A new aspect concerning chromone chemistry leading to the one-pot synthesis of functionalized novel ABCD-fused chromenopyrazolopyridines has been described. The synthesis involves a multicomponent reaction of chromone-3-benzoylhydrazones with isocyanides and acetylenedicarboxylates, whereupon novel complex tetracyclic benzopyrone derivatives containing three stereogenic centres were formed. The structure elucidation of the products was accomplished by 1D and 2D NMR experiments and confirmed by X-ray crystallographic analysis. Full assignment of all ¹H and ¹³C NMR chemical shifts has been unambiguously achieved. The reaction mechanism is also discussed. In addition, eight chromenopyrazolopyridine derivatives were tested for possible biological activity (antioxidant and lipid peroxidation inhibition).     

One-pot synthesis of novel fused pentacyclic chromenopyrimidobenzimidazolones and benzimidazolyl-chromenyl-substituted thiazolidinones

The ultrasound promoted synthesis of a number of novel fused pentacyclic chromenopyrimido[1,2-α]benzimidazolones by the one-pot reaction of 3-formylchromones with 2-aminobenzimidazole is described. Moreover, the isolated pentacyclic chromone derivatives upon microwave irradiation with 2-mercaptocarboxylic acids afforded benzimidazolyl-chromenylthiazolidinones incorporating three pharmacophoric heterocycles; the same thiazolidinones were also formed through a multicomponent reaction under microwave irradiation involving 3-formylchromones, aminobenzimidazole and 2-mercaptocarboxylic acids. The structural elucidation of the products was accomplished by 1D and 2D NMR experiments and for thiazolidinones was also confirmed by X-ray crystallographic analysis. Full assignment of all ¹H and ¹³C NMR chemical shifts has been unambiguously achieved. The proposed reaction mechanism is also discussed.     

Expeditious one-pot synthesis of highly substituted thiazolo[3,2-a]pyridines involving chromones

The 1,4-zwitterion derived from 4,5-dimethylthiazole and acetylenedicarboxylates has been shown to react at low temperature readily with 3-formylchromones (chromone-3-carboxaldehydes) resulting, after an unusual rearrangement, in the facile synthesis of thiazolo[3,2-a]pyridine derivatives; in the case of electron-donating substituents in the chromone ring tetracyclic chromenothiazolopyridines are isolated as the main reaction products. However, at higher temperature after an unexpected 1,2-aroyl migration 8-formyl-5H-[1,3]thiazolo[3,2-a]pyridines are formed as a mixture of two rotamers. Structural assignments of the new compounds as well as complete assignment of ¹H and ¹³C NMR signals were based on the analysis of their ¹H and ¹³C NMR (1D and 2D), IR, MS and elemental analysis data. Plausible mechanisms are proposed.     

Reaction of 5-halo-1,2,3-thiadiazoles with aliphatic diamines. Synthesis and intramolecular cyclization of bis(1,2,3-triazolyl-1,2,3-thiadiazolyl)sulfides

Bis[1,2,3]triazolo[1,5-f:5',1'-b][1,3,6]thiadiazepine and [1,5-g:5',1'-b][1,3,7]thiadiazocine ring systems have been synthesized from 5-halo-1,2,3-thiadiazoles and aliphatic diamines. We have found that the last step of the process is the cyclization of initially formed bis(1,2,3-triazolyl-1,2,3-thiadiazolyl)sulfides. The structures of the intermediates and products were supported by different NMR spectroscopic methods (1H coupled 13C NMR, 2D HETCOR, HMBC and 1D INADEQUATE experiments) and mass spectrometry. Differences in the reaction pathway for aliphatic and less nucleophilic aromatic diamines were determined.     

TiCl3 catalyzed one-pot protocol for the conversion of aldehydes into 5-substituted 1H-tetrazole

An efficient protocol has been explored for the one-pot synthesis of tetrazole derivatives with wide functional group compatibility in moderate to very high yields starting from aliphatic and aromatic substituted aldehydes. The reaction proceeds via non-isolated oxime and nitrile intermediates. The structures of the products were confirmed by IR and NMR spectroscopy. A plausible reaction mechanism is also provided.     

Diazatruxenes from the Condensation Reaction of Indoles with Ninhydrin

The reaction of indoles with ninhydrin has been reported to provide only 1:1 condensation products (cf. A or 8 ) that show good antioxidant and anti‐inflammatory activity. In the present work, our synthetic challenge for the synthesis of innovative, highly substituted tetra‐indole indanes of type 1 via a 4:1 condensation reaction in acetic acid gave two unexpected new products, the diazatruxene derivatives 3 and 4 . The novel structures have been characterized by their analytical and spectral data including 1D‐ and 2D‐NMR. With 5‐chloroindole, only the known 1:1 reaction.     

Synthesis of Some New 1,3,2-Oxazaphosphinine, 1,3,2-Diazaphosphinine,Acyclic, and/or Cyclic α-Aminophosphonate Derivatives Containing the Chromone Moiety

The synthesis of some new 1,3,2-oxazaphosphinine 18, 1,3,2-diazaphosphinine 19, acyclic, and cyclic α-aminophosphonate derivatives 3–17 containing the chromone moiety have been achieved via reaction of 3-(phenyliminomethyl)chromone (1), 3-(phenylaminomethylene)-2-hydroxychromanone (4), and/or 3-(phenylamino-methylene)-2-(phenylamino)chromanone (5) with diethyl phosphite, tris(2-chloroethyl)phosphite, and phenylphosphonic dichloride. Structures of the products were verified on the basis of their elemental analyses, IR, ¹H, and ³¹P NMR spectral data.     

3-Benzoyl-3,4-dihydro-2H,5H-1-benzopyrano[4,3-b]pyran-5-ones by condensation of 4-hydroxycoumarins with enone mannich bases

Starting from 4-hydroxycoumarins 4 and 1-aryl-2-(dimethylaminomethyl)prop-2-en-1-ones 2 the title compounds 6 have been synthesized. The reaction is initiated by addition of the C-3 carbon atom of 4-hydroxycoumarin to the enone double bond of the Mannich base, subsequent deamination affords the intermediate 3-(2-benzoylallyl)-4-hydroxycoumarin 8 , followed by ring closure. Depending on the reaction time, varying proportions of the ketones 6 and 8 are formed and support the mechanism defined. The spectroscopic data of all products unambiguously distinguish between the coumarin and the chromone structures in favor of the former.     

Two New Chromone Glycosides from Selaginella uncinata

Two new chromone glycosides,5-hydroxy-2,6,8-trimethylchromon-7-O-β-D-gluco-pyranoside,named uncinoside A;5-acetoxy-2,6,8-trimethylchromone-7-O-β-D-glucopyranoside, named uncinoside B,and a known chromone compound named 8-methyl eugenitol were isolated from Selaginella uncinate. Their structures were elucidated by spectra analysis of FAB-MS,1D NMR and 2D NMR including ^1H NMR,^13C NMR,HMQC,HMBC and single-crystal X-ray diffraction techniques.     

Structure elucidation of the intermediate in triethylborane-mediated radical addition of oxime ethers with 2D- and 3D-DOSY NMR

The structures of the components in the triethylborane-mediated radical addition reaction of oxime ether were investigated by 1H- and 3D-DOSY NMR methods. It has been impossible to physically separate the unstable intermediates; therefore, the structures were thus far unidentified. It has been possible to elucidate the structures of these unstable intermediates using Diffusion-Ordered Spectroscopy (DOSY) methods for the reaction in an NMR tube. The DOSY methods resolved the spectra of each starting compound, intermediate and product having different diffusion coefficients. The structure of the intermediate was shown to be due to the bonding of diethylborane to the nitrogen atom of the alkoxyamino group.     

New Secondary Metabolites from Asphodelus tenuifolius

Asphorins A and B ( 1 and 2 , resp.), two new triterpene glycosides, have been isolated along with a new chromone, 3 , from the AcOEt subfraction of the MeOH extract of the whole plant of Asphodelus tenuifolius. Their structures were elucidated by spectral analysis including 2D‐NMR spectroscopic experiments.     

固体酸Amberlyst 15催化合成3-吲哚取代的苯酞类化合物

室温下, 以吲哚和邻甲酰苯甲酸为原料, 通过Amberlyst 15 (15 wt%)催化的傅-克反应, 高产率合成得到一系列3-吲哚取代的苯酞类化合物. 并通过1H NMR, 13C NMR, 红外光谱, 高分辨质谱确证了产物的结构.     

A new and green approach for regiospecific synthesis of novel chromeno-triazolopyrimidin using tungstic acid immobilized MCM-41 as a reusable catalyst

A novel, eco-friendly and fast route has been developed for the synthesis of new and known triazolo[1,5-a]pyrimidin fused chromone derivatives via a one pot three-component reaction of 3-amino-1,2,4-triazoles, aromatic aldehydes and 4-hydroxycoumarin in aqueous medium at room temperature. These reactions are catalyzed by MCM-41-HWO₄ as a safe and recyclable mesoporous solid acid. It combines successfully the synergistic effect of green chemistry with nanocatalysis. The yields are high and the products were characterized by ¹H NMR, ¹³CNMR spectra and elemental analysis.     

无溶剂下位阻控制的Biginelli反应

在NaHSO4作催化剂, 无溶剂下将水杨醛、活泼亚甲基化合物和尿素或硫脲进行Biginelli 反应, 高收率地合成了一系列monastrol类物质. 产物的结构通过IR, 1H NMR, 13C NMR光谱数据和单晶解析表征和确定. 对于不同活泼亚甲基化合物参与的反应, 形成了4-(2-羟基苯基)嘧啶衍生物2和氧桥嘧啶衍生物3两类物质, 活泼亚甲基化合物分子中醇酯基的结构是决定两种嘧啶衍生物结构的主要因素. 对于以前报道的Biginelli产物4-(2-羟基苯基)嘧啶衍生物2a和氧桥嘧啶衍生物3e的形成也进行了讨论.     

The charge delocalised beta,beta-carotene dication--preparation, structure elucidation by NMR and reactions with nucleophiles

The reaction between beta,beta-carotene and BF3-etherates has been investigated, leading to structural elucidation of the blue product, formed in appropriate organic solvents, as a symmetrical charge delocalised dication (lambda(max) 985 nm at room temperature in CHCl3) with considerable stability. The reaction, monitored by EPR studies at -25 degrees C, occurred via free radical intermediates. A C40H56BF3 intermediate was captured by EIMS. The detailed structure of the dication was established by COSY, HSQC, HMBC and 1D and 2D ROESY NMR techniques (600 MHz, CDCl3, -20 degrees C) leading to complete assignments of 1H and 13C chemical shifts and 3J(H,H) coupling constants. The effects of the two delocalised charges on chemical shift (charge distribution) and bond distance (3J(H,H)) were considered. The results are consistent with charge delocalisation mainly in the C-5-C-9 and C-5'-C-9' regions and with bond inversion to retro shifted double bonds in the central C-13-C-13' region. A convention for denoting the charge delocalisation and bond types is presented. The experimental results are discussed relative to previous theoretical calculations of the beta,beta-carotene dication structure. (All-E) and (15-Z)-beta,beta-carotene provided the same dication. The NIR spectra and stability of dications prepared in the same manner from the related carotenes 20,20'-dinor-beta,beta-carotene, heptapreno-beta,beta-carotene and nonapreno-beta,beta-carotene were examined for comparison. Reactions of the beta,beta-carotene dication with selected nucleophiles provided products including isocryptoxanthin, isocarotene and mutatochrome with H2O as nucleophile, and isocryptoxanthin methyl ether, 8-methoxy-7,8-dihydro-beta,beta-carotene and isocarotene with CH3ONa as nucleophile. The formation of these products is rationalised from the structure assigned to the dication.     

含P_H键苯并磷杂环化合物与醛反应的研究

利用含P_H键苯并磷杂环化合物与醛的反应,设计合成了新的A2羟基膦酸衍生化喹唑啉酮含磷类似物2或Ò,并研究了含P_C_O结构的2或Ò转化为含P_O_C结构的3或Ó的重排反应,目标化合物的结构经NMR,IR,MS和元素分析证实.结合NMR数据,探讨了化合物2因具有C^*和P^*两个手性中心而产生的非对映异构现象及其氢谱特征.对所合成的化合物进行了初步生物活性测试,发现部分化合物具有很好的抗植物病原真菌(苹果斑点落叶病菌)作用和一定的人体疱疹病毒抑制活性.     

基于配合共保护策略合成γ-L-谷氨酰二肽的新方法

提出了一种采用谷氨酸席夫碱Ni(II)配合物共保护L-谷氨酸的α-氨基和α-羧基合成γ-L-谷氨酰二肽的新方法. 首先由手性助剂——2-[N-(N-苄基-脯氨酰)氨基]二苯甲酮(1)、六水合氯化镍和L-谷氨酸反应, 得到谷氨酸席夫碱Ni(II)配合物2, 产率为98.2%; 进而采用二异丙基碳二亚胺(DIC)/1-羟基-苯并三唑(HOBt)复合缩合剂法分别与L-氨基酸3a～3h反应, 得到相应的γ-L-谷氨酰二肽席夫碱Ni(II)配合物4a～4h, 产率为93.1%～99.0%; 最后稀酸水解配合物, 得到γ-L-谷氨酰二肽5a～5h, 产率为73.0%～86.4%, 高收率(92.2%～97.4%)回收手性助剂. 中间产物和终产物的结构经由旋光, 1H NMR, 13C NMR和HRMS表征.     

A new chromone from seeds of <Emphasis Type="Italic">Cydonia oblonga</Emphasis>

The new chromone 5,7-dihydroxy-2-n-pentacosanylchromen-4-one (1) in addition to the three known compounds ursolic acid (2), tormentic acid (3), and β-daucosterol (4) were isolated from seeds of Cydonia oblonga. Their structures were determined based on their 1D and 2D NMR and HR-ESI-MS spectral data.     

Signs of formation and chemical evolution of zwitterions in the reaction of 1-methylimidazole with cyanophenylacetylene and benzaldehyde

Primary monitoring of the three-component reaction of 1-methylimidazole with cyanophenylacetylene and benzaldehyde by EPR, UV, NMR, and IR spectroscopy has been carried out. Experimental evidence has been obtained for the formation of zwitterions and carbenes of the imidazole series as intermediates of a new functionalization reaction of the imidazole ring leading to 2-benzoyl-3-(1-methyl-1H-imidazol-2-yl)-3-phenylpropanenitrile.