Studies on the synthesis and structural characterization of cyclomercurated ferrocenylimines containing heterocyclic ring

The cyclomercurated ferrocenylimines containing heterocyclic ring can be prepared by the cyclomercuration of acylferrocene, followed by the condensation of the resulting product with the appropriate heterocyclic amine. This procedure provides an efficient method for the synthesis of cyclomerucurated ferrocenylimines containing heterocyclic ring which is difficultly synthesized by the traditional method, i.e. imination and then cyclomercuration. A series of these compounds were synthesized by this new method and characterized. The X-ray crystal structure of [HgCl(η⁵-C₅H₃C(CH₃)=N-2-C₅H₃N-6-CH₃) Fe(η⁵-C₅H₅)] (3d) has been determined and the reaction mechanism was proposed.     

Synthesis of pyrylium salts and pyridines containing heterocyclic substituents

A method of synthesizing pyrylium salts with heterocyclic substituents in the ring, has been investigated. The synthesis was carried out in two stages: alkaline condensation of aromatic and heterocyclic aldehydes with methyl ketones to give 1, 5-diketones, followed by cyclization to pyrylium salts by treatment with triphenylmethyl perchlorate. Pyridines containing heterocyclic substituents were obtained by treating the pyrylium salts with ammonia.     

Ring Closure Reactions of Chalcones Using Microwave Technology

The synthesis of heterocyclic compounds containing pyrimidine, pyrazoline, isoxazoline and cyclohexenone ring from chalcone derivatives containing anisole and 3′4′-methylenedioxy phenyl ring under ‘dry conditions’ using microwaves and by conventional methods are described.     

Heterocyclic Polyimides

This paper presents the synthesis of certain polyimides which contain one of the following heterocycles: oxadiazole, benzox-azinone, benzthiazole. Their properties, particularly thermal stability and hydrolytic stability, are compared to fully aromatic polyimides. Poly-1,3,4-oxadiazole-imides have been synthesized either by the reaction of ditetraeole monomers which contain preformed imide cycles with diacid chlorides, or by the reaction of an aromatic diamine containing a preformed oxadiazole ring with diacid chlorides containing preformed imide rings. Polybenz-oxazinone-imides have been synthesized by polycondensation of a bis(amino acid), 4,4′-diaminodiphenylmethane-3,3′-dicarboxylic acid, with diacid chlorides containing preformed imide rings. Polybenzthiazole-imides have been obtained by polycondensation of aromatic diamines containing a preformed benzthiazole ring with diacid chlorides containing preformed imide rings. Thermal stabilities of these heterocyclic polyimides are similar and in certain cases are higher than those of fully aromatic polyimides. It was also found that the hydrolytic stability of heterocyclic polyimides is definitely superior to that of aromatic polyimides.     

Hydrogen bonded complexes of oxazole family: electronic structure,stability, and reactivity aspects

Structural Chemistry - In the present study, five-membered heterocyclic ring systems containing oxygen with one, two, three, and four nitrogen atoms in the ring along with their isomeric forms and...     

Synthesis of New Sulfur-Substituted Pentacyclic 1,2,4-Triazolopyrimidine Derivatives

Russian Journal of Organic Chemistry - Pentacyclic heterocyclic compounds containing a 1,2,4-triazole ring have been synthesized from...     

Novel thieno[2,3-d]pyrimidines: their design, synthesis, crystal structure analysis and pharmacological evaluation

Novel thieno[2,3-d]pyrimidines containing a cyclohexane ring fused with a six- or five-membered heterocyclic moiety along with a benzylic nitrile were designed as potential inhibitors of PDE4. Expeditious synthesis of these compounds was carried out via a multi-step sequence consisting of a few key steps such as Gewald reaction, Dieckmann type cyclisation and Krapcho decarboxylation. This newly developed strategy involved construction of the thienopyrimidine ring followed by the cyclohexanone moiety and subsequently the fused heterocyclic ring. A number of thieno[2,3-d]pyrimidine based derivatives were synthesized using this method some of which showed promising PDE4B inhibitory properties. One of them was tested for PDE4D inhibition in vitro and dose dependent inhibition of TNF-α. A few selected molecules were docked into the PE4B protein the results of which showed good overall correlations to their observed PDE4B inhibitory properties in vitro. The crystal structure analysis of representative compounds along with hydrogen bonding patterns and molecular arrangement present within the molecule is described.     

Micro-eta3:eta4-Lithiocene and eta3:eta3-zincocene incorporating 1,2-diaza-3,5-diborolyl, a cyclopentadienyl analog

A heterocyclic cyclopentadienyl analog containing only one carbon atom in the ring was prepared and a polymeric lithiocene and a monomeric zincocene containing this novel ligand have been isolated and crystallographically characterized.     

Synthesis and antimicrobial evaluation of some heterocyclic chalcone derivatives

Some new heterocyclic compounds containing isoxazole, pyrazole and oxadiazole ring systems were prepared from various chalcones. The synthesized compounds have been characterized by elemental analysis and spectral methods. These compounds were screened for their antimicrobial activities.     

Synthesis of trifluoromethylated azines via nucleophilic oxidative substitution of hydrogen by trifluoromethyl carbanions

A novel, three-step method of trifluoromethylation of azines via oxidative nucleophilic substitution of hydrogen in the heteroaromatic ring by a CF3- carbanion is presented. The key reaction of this process is the addition of the CF3- carbanion, generated by treatment of Me3SiCF3 with KF(s) and Ph3SnF catalyst, to N-alkylazinium salts. The resulting dihydroazines containing a trifluoromethyl group are relatively stable compounds and can be isolated in a pure form. Deprotection of the N-p-methoxybenzyl substituent and aromatization of the heterocyclic ring upon treatment with CAN provides azines with a CF3 group in the ring position originally occupied by hydrogen. The whole process can be thus considered as a nucleophilic oxidative displacement of hydrogen by a CF3- carbanion.     

Synthesis of a novel purine‐containing heterocyclic ring system: 8,10‐Dimethylindolo[2′,3′:5,6][1,2,4]triazino[4,3‐f]purine‐9,11(8H, 10H, 13H)‐dione

The preparation of a novel purine containing heterocyclic ring system, indolotriazinopurine, by the condensation of 8‐hydrazinotheophylline with 5‐substituted isatins via the intermediate hemiaminal and hydrazone derivatives, is described.     

Approaches to Total Synthesis of Heterocyclic Steroidal Systems

In heterocyclic steroids the carbon atoms of the steroid skeleton (positions I to 17) are replaced in part by hetero atoms. The term generally denotes compounds containing one or two nitrogen, oxygen, and/or sulfur atoms. The part of the molecule containing the hetero atom is either introduced as a preformed unit or is constructed by stepwise synthesis. The examples given in the present article contain the hetero atoms in ring A, ring B, between rings A and B, and/or between rings C and D.     

7- and 8-membered ring sugars and related systems : 7-Membered rings from diolefins derived from dioxepans via double michael condensations

The possibilities of cyclisation to 7-membered ring sugars containing nitro- and cyano-functions via double Michael condensations of diolefins derived from sugar dioxepans was investigated. With nitromethane cyclised products were obtained while with the larger ethyl cyanoacetate and malononitrile only one double bond was attacked without cyclisation. Treatment of the diolefins with excess ammonia resulted in cyclisation to novel heterocyclic systems containing oxygen and nitrogen often of known stereochemistry; with butylamine no cyclisation occurred. Treatment with hydrogen sulphide also resulted in cyclisation to novel heterocyclic systems containing sulphur and oxygen often of known stereochemistry. In these systems cyclisation only occurs with the smaller reagents.     

Thermodynamic analysis of strain in the five-membered oxygen and nitrogen heterocyclic compounds

Cyclopentane is conventionally strained. Replacement of a carbon atom by a heteroatom obviously impacts angular strain in the five-membered ring compounds. Changes of strains in the five-membered cycles are also caused by a double bond or atttached benzene rings. We studied the thermochemical properties of Indane, 2,3-dihydrobenzofuran, indoline, N-methyl-indoline, carbazole, and N-ethyl-carbazole to obtain a better quantitative understanding of the energetics associated with these compounds containing five-membered ring units. We used combustion calorimetry, transpiration method, and high-level first-principles calculations to derive gaseous enthalpies of formation of the five-membered heterocyclic compounds. Our new values together with the selected values for parent heterocyclic compounds, available from the literature, were used for calculation of the strain energies H(S) of five-membered C-, N-, and O-containing cycles. Quantitative analysis of the resulting stabilization or destabilization of a molecule due to interaction of benzene rings with the heteroatom has been performed.     

五元氮杂环的开环反应研究进展

综述了近年来各种五元氮杂环的开环反应及其在有机合成中的应用。杂环化合物在有机合成中的作用越来越重要,五元氮杂环是其中最重要的一部分,其开环反应可以用来合成某些用其它方法难以合成的多官能团化合物,或通过开环和修饰合成其它环状化合物,还可以作为保护基以及研究仿生合成领域中各类复杂的生化反应等。     

Transformations of bicyclic systems containing an isothiazole ring

Isothiazolium salts, which are readily hydrolyzed to heterocyclic o-formyl disulfides, were obtained by alkylating bicyclic systems containing an isothiazole ring. The initial isothiazole-containing systems are stable in water and react with nucleophiles such as the hydroxyl ion with opening of the isothiazole ring and formation of o-cyanodisulfides.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 223–226, February, 1985.     

Synthesis of heterocyclic thiosulfonates

[formula: see text] A simple synthesis of heterocyclic thiosulfonates containing indole, indoline, benzoimidazole, and quinoxaline rings is described. The synthesis of these thiosulfonates involves the preparation of the appropriately substituted thiols followed by sulfonylation to give thiosulfonates. The corresponding thiols were prepared in a simple and efficient manner by using a thiocyanation reaction either prior to heterocycle ring formation or after heterocycle ring formation. These thiosulfonates were coupled successfully to the 5,6-dihydropyran-2-one ring to give products that showed excellent HIV protease activity.     

Thermodynamics of Exo–Endo Isomerization of Carbon–Carbon Double Bonds in Five-Membered Ring Compounds. A Quantum Chemical Study

The energies and enthalpies of isomerization of methylenecyclopentane to 1-methylcyclopentene, 1,3-dimethylenecyclopentane to 1-methyl-4-methylenecyclopentene, and 3-methylenecyclopentanone to 3-methylcyclopent-3-en-1-one have been determined by DFT calculations at the B3LYP/6-31G* level of theory. Related studies were also carried out for some structurally related five-membered heterocyclic compounds containing one or two O atoms in the ring. The aim of the work was to study how the energetics of the exo endo isomerization of the C=C bond in methylenecyclopentane, 2-methylenetetrahydrofuran and 4-methylene-1,3-dioxolane is affected by replacement of an sp³ hybridized ring C atom with a trigonal one. This effect turned out to be small—only a few kilojoules per mole in carbocycles, favoring the endo isomer; in the heterocyclic compounds, especially those containing two ring O atoms, the effect is much greater.     

Synthesis of heterocyclic analogs of chalcone containing the selenophene ring

Crotonaldehyde-type condensation using alkaline or acid catalyst is used to synthesize 14 chalcone analogs containing in addition to the selenophene ring, a number of other heterocyclic groups. A Michael adduct is shown to be formed by reaction of 2-acetylselenophene with 2-pyridine aldehyde.     

Current perspectives on quinazolines with potent biological activities: A review

Quinazoline is a heterocyclic compound having biological activities. It is aromatic in nature having bicyclic structure containing benzene ring and pyrimidine ring. Quinazoline and its derivatives are found to have wide range of biological activities that is anticancer, analgesic, antimicrobial, antihypertensive, anticonvulsant, antimalarial, antitumor, and anti-tubercular activities. The purpose of this review is to highlight the recent researches made by researchers on various biological activities of quinazoline derivatives on different targets.