Mn(III)-Catalyzed Synthesis of Pyrroles from Vinyl Azides and 1,3-Dicarbonyl Compounds

Synthesis and biological evaluation of panaxadiol ester derivatives possessing pyrazole and pyrrole moiety as HIF-1α inibitors

Hypoxia-inducing factor-1α (HIF-1α) is overexpressed in variety of tumor patients and plays an important role in the regulation of hypoxia response in tumor cells. Therefore, its inhibitors have become one of the targets for the treatment of a variety of cancers. Two series of panaxadiol (PD) ester derivatives containing pyrazole (18a-j) and pyrrole (19a-n) moiety were synthesized and their HIF-1α inhibitory activities were evaluated. Among all the target compouds, compounds 18c, 19d, and 19n (IC50 = 8.70-10.44 μM) showed better HIF-1α inhibitory activity than PD (IC50 = 13.35 μM). None of these compounds showed cytotoxicity above 100 μM and inhibited HIF-1α transcription in a dose-dependent manner. These compounds showed good antitumor activity and provide lead compounds for further design and activity study of PD ester derivatives.

Et2Zn-Mediated Radical (3 + 2) Cycloaddition of Vinyl Azides with Ethyl Iododifluoroacetate to Access 3,3-Difluoro-γ-lactams

A diethylzinc-mediated radical (3 + 2) cycloaddition of vinyl azides with ethyl iododifluoroacetate is presented. The developed reaction features good functional group tolerance, broad substrate scope, and operational simplicity, enabling efficient assembly of a wide range of 3,3-difluoro-γ-lactam derivatives bearing an O-substituted quaternary carbon center in moderate to good yields. The utility of the method is showcased by a scaled-up reaction, conversion of the product, and late-stage structural modifications of a variety of pharmaceutical compounds.

Vinylazides: versatile synthons and magical precursors for the construction of N-heterocycles

Nowadays, application of vinylazides as precursors is a key method for the construction of N-heterocycles in organic synthesis. These versatile three-atom synthons can be converted into intermediates such as 2H-azirines, iminyl radicals, iminyl metal complexes, iminyl inions and nitrilium ions that subsequently afford a wide range of polyfunctional cyclic nitrogen-containing compounds. In this review, the reactions of vinylazides leading to these products (in the last decade) are categorized based on the types of the resulting N-heterocyclic rings and a brief and concise description of the reaction mechanisms is presented.

Silver-Catalyzed Regioselective Synthesis of Highly Substituted 2-Trifluoromethyl Pyrroles

An efficient and regioselective synthesis of highly substituted 2-trifluoromethyl pyrrole derivatives via silver-catalyzed cyclization of vinyl azides with ethyl 4,4,4-trifluoro-3-oxobutanoate is reported. Various α-(heteo)aryl, alkyl, β-aryl, as well as α,β-disubstituted vinyl azides, participate in this transformation. The reaction mechanism likely involves the addition of in situ generated 2H-azirine to the diketone species, followed by intramolecular addition, N-C¹ cleavage, and elimination.

Synthesis of Quinolines via the Metal-free Visible-Light-Mediated Radical Azidation of Cyclopropenes

We report the synthesis of quinolines using cyclopropenes and an azidobenziodazolone (ABZ) hypervalent iodine reagent as an azide radical source under visible-light irradiation. Multisubstituted quinoline products were obtained in 34-81% yield. The reaction was most efficient for 3-trifluoromethylcyclopropenes, affording valuable 4-trifluoromethylquinolines. The transformation probably proceeds through the cyclization of an iminyl radical formed by the addition of the azide radical on the cyclopropene double bond, followed by ring-opening and fragmentation.

Medicinal attributes of pyridine scaffold as anticancer targeting agents

Background

The heterocyclic compounds particularly pyridine displayed clinical and biological implementation. Pyridine scaffolds have been detected in most relevant drug molecules that included pyridine provided a great possibility for treatment.

Main text

Pyridine-containing compounds have increasing importance for medicinal application as antiviral, anticholinesterase activities, antimalarial, antimicrobial, antidiabetic and anticancer. This has generated concern among researchers in synthesising a variety of pyridine derivatives.

Conclusion

This review focuses on different pyridine targets as anticancer and their pharmacophoric elements controlling its activity.

Visible-light-mediated synthesis of quinolines

Visible light promoted synthetic routes of quinolines using different strategies are hereby documented.

Indium(III) Catalyzed Reactions of Vinyl Azides and Indoles

Indium trichloride catalyzes the reaction of vinyl azides with unfunctionalized indoles to give vinyl indoles. This is the first example of displacement of the azide group by a carbon nucleophile while preserving the vinyl function. The protocol employs very mild reaction conditions and offers excellent yields of diverse 3-vinyl indoles. It is amenable to gram scale. Access to a library of 3,3'-bis(indolyl)methanes through condensation of vinyl azides with 2 equiv of an indole is demonstrated.

Azido-Enolonium Species in C-C and C-N Bond-Forming Coupling Reactions

Vinyl azides react with boron trifluoride activated Koser's hypervalent iodine reagent to afford azido-enolonium species. These previously unknown azido-enolonium species react efficiently with aromatic compounds, allyltrimethylsilane, and azoles under mild conditions, with no need for a transition-metal catalyst, forming C-C and C-N bonds to give a variety of α-functionalized ketones. The intermediacy of the proposed azido-enolonium species is supported by spectroscopic studies.

Nickel(ii)-catalyzed C–C, N–C cascade coupling of ketonitriles into substituted pyrroles and pyridines

The first example of nickel complexes as effectively catalyst to C–C, N–C cascade coupling of ketonitriles with arylboronic acids, affording 2,5-diarylpyrroles and 2,6-diarylpyridines.

Visible Light Photoredox-Catalyzed α-Alkylation of Cyclic Tertiary Arylamines

An efficient method was successfully developed to obtain cyclic β-amino ketones via visible-light photoredox catalysis. With this catalytic system, vinyl azides and N-Ph pyrrolidines react to form cyclic β-amino ketones by α-amino radical addition. This method provides a simple, mild, straightforward, and novel paradigm to prepare important β-amino ketones.

Recent advances in iminyl radical-mediated catalytic cyclizations and ring-opening reactions

Iminyl radicals have emerged as versatile synthons for N-heterocycle constructions and ring-opening reactions.

Design, synthesis andin vitroα-glucosidase inhibition of novel coumarin-pyridines as potent antidiabetic agents

Herein, novel coumarin-pyridine derivatives4a–pas potent α-glucosidase inhibitors were synthesized by a one-pot and three-component synthesis method.

Reagent-controlled regiodivergent intermolecular cyclization of 2-aminobenzothiazoles with β-ketoesters and β-ketoamides

Two regiodivergent approaches to intermolecular cyclization of 2-aminobenzothiazoles with β-ketoesters and amides have been developed, controlled by the reagents employed. With the Brønsted base KOt-Bu and CBrCl3 as radical initiator, benzo[d]imidazo[2,1-b]thiazoles are synthesized via attack at the α-carbon and keto carbon of the β-ketoester moiety. In contrast, switching to the Lewis acid catalyst, In(OTf)3, results in the regioselective nucleophilic attack at both carbonyl groups forming benzo[4,5]thiazolo[3,2-a]pyrimidin-4-ones instead.

Catalyst-Free Synthesis of 2,4-Disubstituted-1H-imidazoles through [3 + 2] Cyclization of Vinyl Azides with Amidines

A facile and efficient route for the synthesis of 2,4-disubstituted imidazoles from benzimidamides and vinyl azides through [3 + 2] cyclization under catalyst-free conditions has been described. The method is compatible for a broad range of functional groups with good to excellent yields.

α-Substituted vinyl azides: an emerging functionalized alkene

Vinyl azides are highly versatile synthons that provide access to numerous N-heterocycles and other functional groups.

Synthesis of quinazolinones via radical cyclization of α-azidyl benzamides

Under visible light irradiation with N-bromosuccinimide, α-azidyl benzamides can be transformed into quinazolinones in high efficiency via cascade radical processes.

Visible-light-promoted iminyl radical formation from vinyl azides: synthesis of 6-(fluoro)alkylated phenanthridines

An efficient strategy assisted by visible-light-promoted iminyl radical formation has been developed for the synthesis of 6-(fluoro)alkylated phenanthridine derivatives. In the reactions, addition of alkyl and trifluoromethyl radicals onto vinyl azides gives iminyl radicals, which then undergo intramolecular homolytic aromatic substitution leading to phenanthridines. These reactions can be carried out under mild conditions with high chemical yields and broad substrate scope.

Copper-catalyzed radical coupling of 1,3-dicarbonyl compounds with terminal alkenes for the synthesis of tetracarbonyl compounds

A novel and efficient copper-catalyzed radical cross-coupling of 1,3-dicarbonyl compounds with terminal alkenes for the synthesis of tetracarbonyl compounds with a quaternary carbon atom has been developed. Mechanistically, this transformation involves the construction of two C-C bonds and two C[double bond, length as m-dash]O bonds in a one-pot process. The reaction tolerates a wide range of functional groups and proceeds under mild conditions.

Copper-catalyzed oxidative cyclization of vinyl azides with benzylic Csp3–H bonds for the synthesis of substituted phenanthridines

A copper-catalyzed oxidative cyclization of vinyl azides with benzylic C_sp3–H bondsviaa tandem dual C–H functionalization process has been developed. This reaction allows access to substituted phenanthridines containing a variety of functional groups.

Active methylenes in the synthesis of a pyrrole motif: an imperative structural unit of pharmaceuticals, natural products and optoelectronic materials

Pyrrole is one of the most important azaheterocycles, due to its wide range of applications in pharmaceuticals and optoelectronic materials, coupled with its utility as an intermediate in natural products.