Functionalized pyrano [2, 3-c] pyrazoles were synthesized from 2, 4-dihydro-3H-pyrazol-3-ones, active carbonyl compounds and tert-BuOH in the presence of trifluoroacetic acid at 65 C. These reactions are proceeded by acid catalyzed generation of isobutylene from tert-BuOH for LUMO diene-controlled inverse [4+ 2] cycloaddition reaction with in situ-generated vinylidenepyrazolones.
An ultrasound-promoted green protocol to access a new series of spirocyclopropanes from indeno[1,2-b]quinoxaline derivatives and azomethine ylides, generated in situ from iodine-catalyzed reaction of acetophenones as well as 2-methylquinoline with pyridine in the presence of a base, is described. These transformations proceeded via a spirocyclopropanation reaction followed by elimination of pyridine. Clear evidence for the structure of a spirocyclopropane-linked indenoquinoxaline derivative was obtained from single-crystal X-ray analyses. The most important feature of this reaction is the fact it forms three stereogenic centers, one of which is quaternary with excellent selectivity.
The Huisgen zwitterionic intermediates, generated in situ from N-heterocycles and acetylenic esters were intercepted by tryptanthrins to afford novel spiroindolo[2,1-b]quinazoline-6,2'-pyrido[2,1-b][1,3]oxazines in CH2Cl2 at room temperature. Clear evidence for the structure of a derivative was obtained from single-crystal X-ray analyses. The most important feature of this reaction is the fact it forms two stereogenic centers, one of which is quaternary with remarkable diastereoselectivity.
A novel copper-catalyzed [3+2] cycloaddition reaction with concomitant in situ generation of benzoylacrylonitriles and nitrile imines from phenacylmalononitriles and hydrazonoyl chlorides, respectively, is reported. The reaction was performed using copper(I) chloride as catalyst and N-methylimidazole as a clean complexing agent/weak base to afford the functionalized 4-benzoyl-5-cyanopyrazoles in moderate to good yields and excellent regioselectivity under ambient conditions. This method provides rapid access to a wide range of highly functionalized 4-benzoyl-5-cyanopyrazoles.
A synthesis of β‐ketonitriles by cyanation of aryl methyl ketones with two completely distinct sources of cyanide, namely Me3SiCN and KCN, under metal‐ and oxidant‐free electrochemical anodic oxidation conditions is described. In this approach, a range of β‐ketonitriles can be obtained in good yields. This conversion is facilitated by I2, generated in situ from electrochemical oxidation of iodide ion to afford the β‐ketonitriles. This environmentally benign method is more convenient and practical compared to previous approaches.
A synthesis of β-ketosulfones via sulfination of aryl methyl ketones and aryl acetylenes with sodium sulfinates under mild electrochemical conditions, in moderate to good chemical yields, is described. In particular, an electrochemical sulfination reaction of alkynes with sulfinate salts has never been explored. An environmentally friendly characteristic of this reaction is that it uses electricity as a valuable energy source for electrochemical synthesis of β-ketosulfones. This strategy is more convenient and practical compared to previous approaches.
The zwitterionic intermediates, generated in situ from Ph 3 P and dialkyl acetylenedicarboxylates, are trapped by N–H acidic 2-(alkylamino)-2-(1, 3-dioxo-1H-inden-2 (3H)-ylidene) acetonitriles in refluxing toluene to afford dialkyl 2-alkyl-1-cyano-9-oxo-3, 9-dihydro-2H-indeno [2, 1-c] pyridine-3, 4-dicarboxylates in good yields. The structure of a typical product was confirmed by X-ray crystallography.
With the aim of obtaining new antitumor agents, a series of bis‐quinazolin‐4(3H)‐ones (3a‐3?f) were designed and synthesized. These products contain 4‐oxo‐1,2,3,4‐tetrahydro‐quinazoline and 3H‐quinazolin‐4‐one moieties linked together via a propyl chain. Cytotoxic activities of 3a‐3?f were evaluated against lung adenocarcinoma (A549), breast carcinoma (MCF‐7) and ovarian cancer (SKOV3) cell lines using MTT method. Cisplatin was used as a positive control. Among the tested compounds 3a, 3b, and 3e showed the best cytotoxic activities against all cancerous cell lines with IC50 values even less than cisplatin. Compounds 3d and 3f also showed desirable cytotoxic activities especially against A549 and MCF‐7.
A one-pot synthesis of spiro-heterocyclic systems containing a 1, 2, 4-triazolidine moiety via 1, 3-dipolar cycloaddition reaction of azomethine ylides (generated in situ from α-amino acids and ninhydrin) with diisopropyl azodicarboxylate in 50% aqueous MeOH at room temperature, is described. The structure of a typical product was confirmed by X-ray crystallography. The 1H NMR spectra of diisopropyl 1, 3-dioxo-1, 3-dihydrospiro [indene-2, 3′-[1, 2, 4] triazolidine]-1′, 2′-dicarboxylate exhibited dynamic NMR effects, which were attributed to the fast positional change of the ester groups and their interaction with N–H as well as with methylene protons, and restricted bond rotation of the carbamate groups. The calculated free-energy
The reaction between dialkyl 8-oxo-8H-cyclopenta[a]acenaphthylene-7,9-dicarboxylates and zwitterionic intermediates, generated in situ from alkyl isocyanides and dialkyl acetylenedicarboxylates, is described. This reaction leads to the formation of tetraalkyl 5′-(alkylimino)-5′H-spiro[cyclopenta[a]acenaphthylene-8,2′-furan]-3′,4′,7,9-tetracarboxylates. The structure of a typical product was confirmed by X-ray crystallographic analysis.
Abstract 5-Arylidene-1-methyl-2-thiohydantoins undergo [3+2]-cycloaddition reaction with nitrile imines, generated in situ from hydrazonyl chlorides, at C=C and C=S dipolarophiles in the thiohydantoin moiety to afford thioxo-tetraazaspiro[4.4]nonenones and thia-tetraazaspiro[4.4]nonenones in moderate to good yields. The stereochemistry of these spiroheterocycles has been confirmed by X-ray diffraction studies. Graphic abstract
An efficient method has been developed for the synthesis of 3-[(2-amino-4-arylthiazolium-5-yl)(aryl)methyl]-2-oxo-2H-1-benzopyran-4-olates via a tandem reaction involving 4-hydroxycoumarin, benzaldehydes, thiourea, and 2-bromo-1-arylethan-1-ones, using p-toluenesulfonic acid as catalyst in glacial acetic acid under reflux. The identity of the parent product was confirmed by X-ray analyses while the other similar derivatives were identified by NMR. The good yields of the products, regioselectivity, and lack of metal promoters are the main advantages of this protocol.HighlightsThe reaction of 4-hydroxycoumarin, thiourea, benzaldehydes, and 2-bromo-1-arylethan-1-ones leads to the formation of functionalized 3-[(2-amino-4-arylthiazolium-5-yl)(a
Abstract A regioselective 1,3-dipolar cycloaddition of nitrilimines, generated from hydrazonoyl chlorides, with both C = C double bonds of cyclopentadienone moiety of cyclopenta[a]acenaphthylen-8-ones in the presence of Et3N is described. This dual cycloaddition reaction affords a nearly 3:2 mixture of symmetrical and unsymmetrical hexacyclic bis-dihydropyrazol derivatives in good yields. The stereochemistry of diethyl 3,7-bis(4-chlorophenyl)-4-oxo-1,5-diphenyl-1H-naphtho[1′,8′:4,5,6]pentaleno[1,6a-c:3a,3-c′]dipyrazole-3a,4a(4H,5H)-dicarboxylate was established by X-ray crystallography. Graphic abstract
A convenient regio- and diastereoselective synthesis of functionalized 5a,5b-dihydro-5H,13H-naphtho[1′′,8′′:4′,5′,6′]pentaleno[1′:3,4]pyrrolo[2,1-a]isoquinolin-5-ones via 1,3-dipolar cycloaddition reaction of 8H-cyclopenta[a]acenaphthylen-8-ones with carbonyl-stabilized isoquinolinium N-ylides, is described. Based on DFT calculations at b3lyp/6-311+g(d,p) level of theory, a nonconcerted mechanism is proposed to explain the regioselectivity of this reaction. The structure of a typical product was confirmed by X-ray crystallographic analysis.
N-Methylimidazole (NMI) can act as a masked HCN in the synthesis of 1,3-disubstitued-1H-1,2,4-triazoles via a formal cycloaddition reaction of hydrazonoyl chloride with NMI. The product was proved to be formed via an initial nucleophilic substitution of hydrazonoyl chloride with NMI following cyclization and two sequential C–N bond cleavages.
Abstract Diazo-transfer reaction of tosyl azide and alkyl 2-cyanoacetates in the presence of pyridine at 0??C gives the corresponding alkyl 2-cyano-2-diazoacetates. This material readily undergoes nucleophilic attack by pyridinium 1-cyano-2-alkoxy-2-oxoethan-1-ide to form dialkyl (Z)-3-amino-2-cyano-4-diazopent-2-enedioates. The X-ray structure of a typical product is reported, as well as DFT computational studies that illuminate the structural features of these stable diazo compounds. Graphic abstract
A novel deep eutectic solvent system was prepared by mixing choline chloride as a hydrogen-bond acceptor with 2, 2-bis (hydroxymethyl) propane-1, 3-diol (pentaerythritol) as a hydrogen-bond donor. This green solvent was used for the one-pot synthesis of pyran and chromene derivatives from aromatic aldehydes, 1, 3-dicarbonyl compounds, and malononitrile. The solvent was readily recycled and can be reused three times without significant loss of activity or mass. This procedure offers advantages such as environmental friendliness, shorter reaction times, and higher yields.
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