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The present review has highlighted the chemistry of pyrimido[1,2-a]pyrimidine compounds as one of the most important classes of heterocyclic systems. The main sections include: (1) The synthesis of pyrimido[1,2-a]pyrimidines, (2) reactivity of the substituents attached to the carbon and nitrogen atoms of the ring and (3) biological applications. A discussion demonstrated that the proposed mechanisms of unexpected synthetic routes were intended. The purpose of this review is to provide an overview of the chemistry of pyrimido[1,2-a]pyrimidines to date, in which the compounds should be widely applied in medicinal and pharmaceutical chemistry based on the significant, variable and potent biological results of pyrimidopyrimidine and pyridopyrimidine analogs. This survey will assist scientists in the organic and medicinal chemistry fields to design and develop procedures for the construction of new standard biological compounds.

Heterocycles incorporating a pyrimidopyrimidine scaffold have aroused great interest from researchers in the field of medical chemistry because of their privileged biological activities; they are used as anti-bacterial, antiviral, anti-tumor, anti-allergic, antihypertensive, anticancer, and hepatoprotective agents. Therefore, the present study aims to investigate the chemistry of heterocycles incorporating pyrimido[1,6-a]pyrimidine and pyrimido[1,6-c]pyrimidine skeletons and their biological characteristics. The main sections discuss (1) the synthetic routes to obtain substituted pyrimidopyrimidines, pyrimido[1,6-a]pyrimidin-diones, pyrimidoquinazolines, tricyclic, tetracyclic, and binary systems; (2) the reactivity of the substituents attached to the pyrimidopyrimidine skeleton, including thione and amide groups, nucleophilic substitutions, condensations, ring transformations, and coordination chemistry; (3) compounds of this class of heterocycles containing a significant characteristic scaffold and possessing a wide range of biological characteristics.

The aim of this work is to discuss the chemistry of pyrido[3,4-d]pyrimidines as one of the most important heterocyclic compounds with remarkable synthetic, biological and medical applications. In this overview, the chemistry of heterocyclic compounds incorporated the pyrido[3,4-d]pyrimidine scaffold as demonstrated by chemical reactions and different preparation processes. The anticipated compounds were synthesized from pyridine or pyrimidine compounds and a description of the reactivity of substituents attached to ring carbon and nitrogen atoms is discussed. On the other hand, the synthesis and reactions of fused heterocycles incorporated pyrido[3,4-d]pyrimidine scaffold is described. The diamine analogs included pyrido[3,4-d]pyrimidine core were reported as tyrosine kinase inhibitors. The chemical reactions of certain unexpected and chemically substantial compounds have been discussed.

The present study describes recent advances in the chemistry of heterocycles incorporated oxazolo[4,5-b]pyridine and oxazolo[5,4-b]pyridine skeletons. The main sections included the synthesis of th...

The present review highlights the synthetic procedures reported for the preparation of oxazolo[3,2-a]pyridines as a class of 5-6 bicyclic heterocycles with a nitrogen atom at the ring junction. The...

The present study provides an overview of the chemistry and biological significance of pyrimido[4,5-d]pyrimidine and pyrimido[5,4-d]pyrimidine analogs as types of bicyclic [6 + 6] systems. The main sections include: (1) synthesis methods; (2) the reactivities of the substituents linked to the ring carbon and nitrogen atoms; and (3) biological applications. A discussion demonstrating the proposed mechanisms of unexpected synthetic routes is intended. The aim of this study is to discuss the synthetic significance of the titled compounds and to establish the biological characteristics of this class of compounds as studied to date, where the compounds have been applied on a large scale in the medical and pharmaceutical fields. This survey will help researchers in the fields of synthetic organic and medicinal chemistry to undertake and improve new approaches for the construction of new standard biological components.

This review describes the chemistry of 2,3-dihydroxynaphthalene and the related analogues. The synthetic routes reported to obtain the investigated structures are discussed. In addition, the reacti...

4-Formylphenyl benzoate was utilized as a versatile precursor for the construction of new series of heterocyclic scaffolds that contain thiazole and thiazolidin-5-one rings. The antibacterial activity of these scaffolds against two types of bacteria was screened and most of them exhibited good activity. Among the synthesized thiazole derivatives, compounds 5, 6, and 8a showed antibacterial activity close to the standard chemotherapeutic (Ampicillin).

An enantio-selective l -histidine imprinted polymeric resin was fabricated and evaluated for enantiomeric resolution of histidine racemate. The polymerizable chiral salicyloyl- l -histidine amide was first synthesized and anchored onto a polymeric resin network via condensation polymerization with resorcinol and formaldehyde. l -histidine template molecules were then extracted out of the resin texture via alkaline hydrolysis of the amide bond using sodium hydroxide. The synthetic steps were monitored by means of instrumental techniques including elemental analysis; mass spectra along with both Fourier transform infrared and nuclear magnetic resonance spectroscopy. In addition, the surface morphologies of both imprinted and non-imprinted resins were visualized using scanning electron microscope and the images indicated a relatively rougher surface in case of the imprinted resin. Also, the complete extraction of the template l -histidine molecules was assured using energy-dispersive X-ray spectroscopy, which indicated the absence of nitrogen upon alkaline treatment of the synthesized l -histidine containing resin. Selective adsorption experiments indicated that the maximum adsorption was achieved at pH 8 and followed the pseudo-second-order kinetic model with extracted amounts of 165 ± 1 and 90 ± 1 mg/g with respect to l - and D-histidine, respectively. Moreover, Langmuir model displayed the best fit with the experimentally obtained isotherm data and the maximum adsorption capacities were 195 ± 1 and 102 ± 1 mg/g with respect to l - and d - histidine, respectively. The enantiomeric resolution of d / l -histidine racemate was also carried out utilizing a column backed with the imprinted resin and the outlet collected solution displayed an optical activity related to 36% d -histidine enantiomeric excess.

In a continuation of our program to develop a new class of antimicrobial and antioxidant agents, 13 novel 3-substituted indole derivatives incorporating biologically active heterocycles were synthesized and evaluated for their in vitro antimicrobial activity. Among the synthesized compounds, 3-(7H-imidazo[2,1-c][1,2,4]triazol-5-yl)-1H-indole showed activity against E. faecalis equal to that of ampicillin and 50% higher activity than ampicillin against S. aureus and B. subtilis. Also, 3-(7H-imidazo[2,1-c][1,2,4]triazol-5-yl)-1H-indole was found to exhibit strong in vitro antifungal activity against Candida albicans, Aspergillus niger, and Penicillium sp. The antioxidant activity of the obtained indole derivatives was also studied using 2,2'-diphenyl-1-picrylhydrazyl and 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid).

This review described the synthetic methods, chemical reactivity and biological applications of furan carboxamide compounds. Furan-carboxamides are reported to have important and variable biologica...

The versatile hitherto reported 3-(1H-indol-3-yl)-1H-pyrazol-5-amine () was synthesized by the reaction of 3-cyanoacetylindole () with hydrazine hydrate in refluxing ethanol and used as a key intermediate for the synthesis of novel pyrazolo[1,5-a]pyrimidines via its reactions with appropriate 1,3-biselectrophilic reagents or through three-component condensations with triethyl orthoformate and compounds possessing an activated methylene group. Besides, the applicability and synthetic potency of () to attain polyfunctionally substituted imidazo[1,2-b]pyrazole, pyrazolo[1,5-a][1,3]diazepine and pyrazolo[1,5-c][1,3,5]thiadiazine derivatives of an expected pharmaceutical interest have been investigated. The mechanistic aspects for the formation of the newly synthesized compounds are discussed.

This review describes a literature survey of 1,3,5-triazepines. The investigated heterocycles were the monocyclic and fused 1,3,5-triazepines. The different sections of the paper cover: theoretical methods, spectroscopy aspects, thermodynamic aspects, synthesis and reactions of the monocyclic and fused heterocycles incorporated into the 1,3,5-triazepine moiety. The biological evaluation of the target compounds are also described as well as their synthetic applications. The reaction mechanisms are discussed.

4-(Thiazol-2-yldiazenyl)-1H-pyrazole-3,5-diamine (2) was prepared by the reaction of 2-thiazolylazomalononitrile (1) with hydrazine hydrate in boiling ethanol and used as key intermediate for the synthesis of polyfunctionally substituted pyrazolo[1,5-a]pyrimidines via its reactions with reagents having 1,3-dielectrophilic centers. Structures of the newly synthesized compounds were established by elemental analysis and spectral data. Representative compounds of the synthesized products were tested and evaluated as antioxidant agents. The results revealed that compounds (3), (4), (5), and (9) displayed promising antioxidant activity compared to the activity of ascorbic acid.

A general mild and efficient protocol for the synthesis of amidochloroalkylnaphthol libraries was achieved utilizing SiO2–ZnCl2 (silzic) as a reusable heterogeneous catalyst via Ritter-type reaction, through one-pot, three-component condensation of various aldehydes, chloroacetonitrile, and β-naphthol under solvent-free reaction conditions. The amidochloroalkylnaphthols were cyclized to its related oxazepinones, and their anticancer and antioxidant activities were studied.

2-Thiazolylhydrazonomalononitrile (1) was used as key intermediate for the synthesis of polyfunctionally substituted heterocycles (e.g. pyridazine, tetrazole, pyrimidines, 1,5-benzo diazepine, benzoimidazo[1,2-a]pyrimidine, triazolo[4,3-a]pyrimidine, pyrazole, pyrazolo[1,5-a]triazines, pyrazolo[1,5-a]pyrimidine and 1,5-benzoxazocine) incorporating thiazole moiety via its reactions with some carbon and nitrogen nucleophiles. Structures of the newly synthesized compounds were established by elemental analysis and spectral data. The mechanistic aspects for the formation of the new compounds were also discussed.

3-(1H-Indol-3-yl)-1H-pyrazol-5-amine 3 was prepared in a quantitative yield by heating 3-(1H-indol-3-yl)-3-oxopropanenitrile 2 in dry ethanol with hydrazine hydrate, and utilized as key intermediate for the synthesis of some new pyrazolo[1,5-a]pyrimidines and pyrazolo[5,1-c]triazines. Structures of the newly synthesized compounds were established by elemental analysis and spectral data and evaluated as antioxidant agents. Most of the tested compounds belonging to the pyrazolo[1,5-a]pyrimidine series exhibited better activities than members of the pyrazolotriazine one.