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Topic Review
Ring-Fused Benzimidazoles and Imidazobenzimidazoles
The entry covers the synthesis and biological activity of ring-fused benzimidazoles, imidazo[4,5-f]benzimidazoles and imidazo[5,4-f]benzimidazoles. Compounds are bioreductive antitumor agents when the fused benzene part is a quinone or iminoquinone. Reactions are categorized according to the cyclization reaction, and include oxidative cyclizations using the t-amino effect. Other cyclizations are onto the 1- and 2-positions of benzimidazoles using cross-dehydrogenative coupling and homolytic aromatic substitution. Many syntheses are transition metal mediated, but others are metal-free using thermal, electrochemical and photochemical conditions.
  • 906
  • 11 May 2021
Topic Review
Phorbas Sponges
Porifera, commonly referred to as marine sponges, are acknowledged as major producers of marine natural products (MNPs). Sponges of the genus Phorbas have attracted much attention over the years. They are widespread in all continents, and several structurally unique bioactive compounds have been identified from this species. 
  • 906
  • 30 Nov 2021
Topic Review
Synthesis of Piperazines by C-H Functionalization
Piperazine ranks as the third most common nitrogen heterocycle in drug discovery, and it is the key component of several blockbuster drugs, such as Imatinib (also marketed as Gleevec) or Sildenafil, sold as Viagra. 
  • 900
  • 22 Oct 2021
Topic Review
Synthesis of m-Aryloxy Phenols
Innovative synthetic methods have been developed for the preparation of m-aryloxy phenols, which has allowed for the preparation of complex m-aryloxy phenols with functional groups, such as esters, nitriles, and halogens, that impart specific properties of these compounds.
  • 882
  • 30 Mar 2023
Topic Review
Sharpless Asymmetric Dihydroxylation
Sharpless asymmetric dihydroxylation is an important reaction in the enantioselective synthesis of chiral vicinal diols that involves the treatment of alkene with osmium tetroxide along with optically active quinine ligand. Sharpless introduced this methodology after considering the importance of enantioselectivity in the total synthesis of medicinally important compounds.
  • 879
  • 03 Apr 2023
Topic Review
Zearalenone and the Immune Response
Zearalenone (ZEA) is an estrogenic fusariotoxin, being classified as a phytoestrogen, or as a mycoestrogen. ZEA and its metabolites are able to bind to estrogen receptors, 17β-estradiol specific receptors, leading to reproductive disorders which include low fertility, abnormal fetal development, reduced litter size and modification at the level of reproductive hormones especially in female pigs. ZEA has also significant effects on immune response with immunostimulatory or immunosuppressive results. This review presents the effects of ZEA and its derivatives on all levels of the immune response such as innate immunity with its principal component inflammatory response as well as the acquired immunity with two components, humoral and cellular immune response. The mechanisms involved by ZEA in triggering its effects are addressed. 
  • 878
  • 26 Apr 2021
Topic Review
Biocompounds in Potato Peel
Potato germplasm is characterized by a huge variability in composition and concentration of secondary metabolites that play a role in increasing plant ability to cope with environmental challenges, due to their reported biocide activity on insects, bacteria, and fungi. Their distribution within the tuber is not uniform: Most of them are concentrated in the peel, made of periderm tissue, whose cell layers contain corky cell walls, which confer protection from phytopathogens, especially during tuber growth and storage. Thus, considering that potato peel is constantly exposed to biotic stresses, it is not surprising that it is a precious source of bioactive compounds, mainly phenolics and alkaloids, which have an enormous potential to deliver new bioprotectors.
  • 877
  • 13 Apr 2021
Topic Review
Withaferin A
Withaferin A (WFA) was identified as the most active phytocompound of the plant Withania somnifera (WS) and as having multiple therapeutic/ameliorating properties (anticancer, antiangiogenic, anti-invasive, anti-inflammatory, proapoptotic, etc.) in case of various diseases.
  • 873
  • 04 May 2021
Topic Review
Phosphorus-Substituted Pyridines
Phosphorus(V)-substituted pyridine was first synthesized by Plazek’s research group in 1936 by a reaction of 2-dimethylaminopyridine with phosphorus trichloride under oxidative conditions. Later, related compounds were obtained by reactions of metalated pyridines with phosphorus-halogen compounds, of pyridinediazonium tetrafluoroborate with phosphorus trichloride, of N-alkoxypyridines with sodium diethyl phosphite and phosphines, and of N-pyridylpyridines with phosphonic acid, by the Michaelis–Arbuzov reaction, Pd(II)-catalyzed phosphorylation of halopyridines, cyclization of phosphorus-containing 3-azatrienes, and the Diels–Alder reaction involving 3-phosphoryl-1-azadienes.
  • 871
  • 20 Mar 2023
Topic Review
The Genus Lagochilus (Lamiaceae)
The genus Lagochilus (Lamiaceae) is native to Central, South-Central, and Eastern Asia. 
  • 870
  • 29 Jan 2021
Topic Review
Synthesis of Cyclic Sulfoximines via C–H Bond Activation
Sulfoximines, a ubiquitous class of structural motifs, are widely present in bioactive molecules and functional materials that have received considerable attention from modern organic chemistry, pharmaceutical industries, and materials science. Sulfoximines have proved to be an effective directing group for C–H functionalization which was widely investigated for the synthesis of cyclic sulfoximines. C–H activation of sulfoximines has been widely considered to be an efficient method to construct complex scaffolds with potential bioactivities, especially since Bolm discovered the first efficient strategy of Rh-catalyzed annulation of sulfoximines and alkynes in 2013.
  • 868
  • 10 Feb 2023
Topic Review
Principles of Prototropic Equilibria
Prototropic tautomers always differ by the positions of labile proton(s) and π-electrons. The number of possible tautomeric forms is an internal property of the tautomeric molecule. It is a consequence of the number of labile protons and the number of conjugated tautomeric sites.
  • 866
  • 01 Nov 2023
Topic Review
Synthesis of Variolins, Meridianins, and Meriolins
Marine natural products are a source of essential significance due to a plethora of highly diverse biological properties. The naturally occurring (aza)indole alkaloids variolin B (1), meridianins (2), and their synthetic hybrids meriolins (3) exhibit potent kinase inhibitory activities.
  • 865
  • 06 Feb 2023
Topic Review
Acyl Oxime Ester
The synthetic strategies of oxime derivatives participating in radical-type reactions have been rapidly developed in the last few decades. Among them, the N–O bond cleavage of oxime esters leading to formation of nitrogen-centered radicals triggers adjacent C–C bond cleavage to produce carbon-centered free radicals, which has been virtually used in organic synthesis in recent years.
  • 865
  • 29 Mar 2023
Topic Review
Wittig Reactions under Sonication Conditions
Carbonyl olefinations are among the most important organic syntheses that form C=C bonds, as they usually have high yields and in addition offer excellent stereoselectivity. Due to these advantages, carbonyl olefinations have important pharmaceutical and industrial applications. These reactions contain an additional step of an α-functionalized carbanion to an aldehyde or ketone to produce alkenes, but syntheses performed using metal carbene complexes are also known. The Wittig reaction is an example of carbonyl olefination, one of the best ways to synthesize alkenes.
  • 861
  • 28 Jun 2023
Topic Review
Terpyridine-Polyamine Bridging Ligand (dint)
The ligand, 4'-(p-(1,5-bis(amino)-3-azapentane)methylphenyl)-2,2':6',2"-terpyridine (dint) contains a terpyridine fragment and a tri-amine fragment, which may allow synthetic differentiation between the tridentate binding sites at both sides and may offer the benefits of polydentate ligands and minimisation of isomeric possibilities upon coordination to metal ions.
  • 837
  • 20 Feb 2021
Topic Review
Synthesis Route of C6F12O
C6F12O is in great demand on the market with its excellent environmental performance and broad application prospects. It is of great significance to the development of a synthetic route for C6F12O, suitable for industrial production.
  • 833
  • 15 Apr 2022
Topic Review
Electrical Mode Gas Sensing
Among small organic molecules, perylene diimides (PDIs) are an important class of materials due to their outstanding thermal, chemical, electronic, and optical properties, all of which make them promising candidates for a wide range of organic electronic devices including sensors, organic solar cells, organic field-effect transistors, and organic light-emitting diodes. This is mainly due to their electron-withdrawing nature and significant charge transfer properties. Perylene-based sensors of this type show high sensing performance towards various analytes, particularly reducing gases like ammonia and hydrazine, but there are several issues that need to be addressed including the selectivity towards a specific gas, the effect of relative humidity, and operating temperature.
  • 828
  • 19 Feb 2021
Topic Review
Metal-Nitrosophenolato Complexes
Metal-nitrosophenolato complexes consist of a metal ion (most commonly copper(II)) flanked by typically two or more 2-nitrosophenolate ligands. The syntheses of them demonstrate a privileged introduction of a nitroso (and a hydroxyl via the Baudisch reaction) group to an aromatic ring. These complexes first appeared in the literature as early as 1939, and a range of applications has subsequently been published. However, optimisations of the preparative sequences were not considered, and as such, the reactions have seldom been utilised in recent years; indeed, there remains confusion in the literature as to how such complexes form.
  • 826
  • 15 Dec 2021
Topic Review
Pd-Catalyzed Homogeneous Tandem Processes
Pd-containing catalytic systems for tandem processes have gained special attention due to their enhanced catalytic properties and their possibility of performing several reactions without the necessity of separating the intermediates.
  • 818
  • 24 Aug 2023
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