Copper(II)-catalyzed synthesis of benzo[f]pyrido[1,2-a]indole-6,11-dione derivatives via naphthoquinone difunctionalization reaction

Development in the Synthesis of Bioactive Thiazole-Based Heterocyclic Hybrids Utilizing Phenacyl Bromide

Heterocyclic hybrid frameworks represent a burgeoning domain within the realms of drug discovery and medicinal chemistry, attracting considerable attention in recent years. Thiazole pharmacophore fragments, inherent in natural products such as peptide alkaloids, metabolites, and cyclopeptides, have demonstrated a broad spectrum of pharmacological potentials. Given their profound biological significance, a plethora of thiazole-based hybrids have been synthesized through the conjugation of thiazole moieties with bioactive pyrazole and pyrazoline fragments. This review systematically presents a compendium of robust methodologies for the synthesis of thiazole-linked hybrids, employing the (3 + 2) heterocyclization reaction, specifically the Hantzsch-thiazole synthesis, utilizing phenacyl bromide as the substrate. The strategic approach of molecular hybridization has markedly enhanced drug efficacy, mitigated resistance to multiple drugs, and minimized toxicity concerns. The resultant thiazole-linked hybrids exhibit a myriad of medicinal properties viz. anticancer, antibacterial, anticonvulsant, antifungal, antiviral, and antioxidant activities. This compilation of methodologies and insights serves as a valuable resource for medicinal chemists and researchers engaged in the design of novel thiazole-linked hybrids endowed with therapeutic attribute.

CuBr-mediated synthesis of 1,4-naphthoquinones via ring expansion of 2-aryl-1,3-indandiones

A CuBr-mediated direct insertion of alkenes into unstrained ring 2-aryl-1,3-indandiones is reported, which provides a one-carbon ring expansion strategy for the synthesis of 1,4-naphthoquinones. Entirely differing from the existing reports, the alkenes herein behave as C1 units to participate in annulation reactions. This transformation provides a facile route to access a class of highly functionalized 1,4-naphthoquinones with good yields, good functional-group tolerance and high atom-economy. Further research on the application of this reaction is currently underway in our laboratory.

Heterocyclic Iminoquinones and Quinones from the National Cancer Institute (NCI, USA) COMPARE Analysis

This review uses the National Cancer Institute (NCI) COMPARE program to establish an extensive list of heterocyclic iminoquinones and quinones with similarities in differential growth inhibition patterns across the 60-cell line panel of the NCI Developmental Therapeutics Program (DTP). Many natural products and synthetic analogues are revealed as potential NAD(P)H:quinone oxidoreductase 1 (NQO1) substrates, through correlations to dipyridoimidazo[5,4-f]benzimidazoleiminoquinone (DPIQ), and as potential thioredoxin reductase (TrxR) inhibitors, through correlations to benzo[1,2,4]triazin-7-ones and pleurotin. The strong correlation to NQO1 infers the enzyme has a major influence on the amount of the active compound with benzo[e]perimidines, phenoxazinones, benz[f]pyrido[1,2-a]indole-6,11-quinones, seriniquinones, kalasinamide, indolequinones, and furano[2,3-b]naphthoquinones, hypothesised as prodrugs. Compounds with very strong correlations to known TrxR inhibitors had inverse correlations to the expression of both reductase enzymes, NQO1 and TrxR, including naphtho[2,3-b][1,4]oxazepane-6,11-diones, benzo[a]carbazole-1,4-diones, pyranonaphthoquinones (including kalafungin, nanaomycin A, and analogues of griseusin A), and discorhabdin C. Quinoline-5,8-dione scaffolds based on streptonigrin and lavendamycin can correlate to either reductase. Inhibitors of TrxR are not necessarily (imino)quinones, e.g., parthenolides, while oxidising moieties are essential for correlations to NQO1, as with the mitosenes. Herein, an overview of synthetic methods and biological activity of each family of heterocyclic imino(quinone) is provided.

Copper(I)-Mediated Divergent Synthesis of Pyrroquinone Derivatives and 2-Halo-3-amino-1,4-quinones

A divergent transformation of 2-amino-1,4-quinones for the synthesis of pyrroquinone derivatives and 2-halo-3-amino-1,4-quinones was disclosed. The mechanistic study showed that both the tandem cyclization and halogenation involved a Cu(I)-catalyzed oxidative radical process. This protocol not only constructed a series of novel pyrroquinone derivatives with high atom economy but also provided a new method of halogenation via directed C(sp²)-H functionalization with CuX (X = I, Br, Cl) serving as the X (X = I, Br, Cl) source.

Recent progress in the synthesis of pyrrolo[2,1-a]isoquinolines

Pyrrolo[2,1-a]isoquinolines occur frequently in a large number of bioactive natural products and pharmaceutically important molecules. The synthesis of pyrrolo[2,1-a]isoquinoline derivatives is an easy and useful way to produce artificial molecules with potential applications. A huge number of excellent methodologies for constructing pyrrolo[2,1-a]isoquinolines have been reported in the last decade. This review summarizes the recent advances in this research field covering from 2011 to 2021.

An efficient diastereoselective synthesis of novel fused 5H-furo[2,3-d]thiazolo[3,2-a]pyrimidin-5-ones via one-pot three-component reaction

Herein, a convenient and efficient synthesis of 7-benzoyl-6-(aryl)-6,7-dihydro-5H-furo[2,3-d]thiazolo[3,2-a]pyrimidin-5-one derivatives was achieved from the reaction of isoquinolinium N-ylides, aromatic aldehydes, and heterocyclic 1,3-dicarbonyl compounds via one-pot three-component diastereoselective domino reaction in good-to-excellent yields. The advantages of this protocol are easily available starting materials, operational simplicity, and avoidance of hazardous organic solvents and catalyst. The synthesized products were characterized by IR, ¹H NMR, ¹³C NMR and mass spectra. Additionally, the conclusive structure of target compounds was confirmed by X-Ray diffraction analysis.

Ruthenium(II)-Catalyzed Double Annulation of Quinones: Step-Economical Access to Valuable Bioactive Compounds

Double ruthenium(II)-catalyzed alkyne annulations of quinones were accomplished. Thus, a strategy is reported that provides step-economical access to valuable quinones with a wide range of applications. C-H/N-H activations for alkyne annulations of naphthoquinones provided challenging polycyclic quinoidal compounds by forming four new bonds in one step. The singular power of the thus-obtained compounds was reflected by their antileukemic activity.

Synthesis of benzonaphthofuroquinones and benzoylnaphthindolizinediones by reactions of flavonoids with dichlone under basylous, oxygenous and aqueous conditions: their cytotoxic and apoptotic activities

Using flavonoids and dichlone as substrates, six benzonaphthofuroquinones and three benzoylnaphthindolizinediones were synthesized through common base-catalyzed method and a new method of combining base-catalyzed with O₂/H₂O exposing.

Crystal structure of 12-(2-hydroxybenzoyl)benzo[f]pyrido[1,2-a]indole-6,11-dione, C23H13NO4

C23H13NO4, monoclinic, P21/n (no. 14), a = 11.6537(6) Å, b = 5.1315(2) Å, c = 26.8047(13) Å, β = 96.266(3)°, V = 1593.4(13) Å3, Z = 4, Rgt(F) = 0.0531, wRref(F2) = 0.1432, T = 90.0(5) K.

Selective synthesis of spirooxindoles via a two-step reaction of N-phenacylpyridinium bromide, 1,3-indanedione and N-alkylisations

The three-component reaction of 1,3-indanedione and N-alkylisatins with two molecular N-phenacylpyridinium salts in dry acetonitrile in the presence of triethylamine resulted in unique functionalized spiro[indoline-3,4'-naphtho[1,2-b]furan] derivatives in good yields, which were successfully converted to spiro[indoline-3,2'-naphthalen]-4'-yl acetate derivatives by acylation with acetyl chloride in methylene dichloride and alkoxy-substituted spiro[benzo[h]chromene-5,3'-indolines] by acid-catalyzed etherification reaction in alcohol. The reaction mechanism involved the sequential cycloaddition of the in situ-generated pyridinium ylide to dipolarophilic enone, ring-opening of 1,3-indanedione, and selective annulation.

Diastereoselective synthesis of spirocyclic isoxazolo[5,4-c]pyrrolo[2,1-a]isoquinolines via cascade double [3 + 2]cycloadditions

The one-pot base-promoted cascade double [3 + 2] cycloaddition reaction of N-cyanomethylisoquinolinium chloride with (E)-3-arylideneindolin-2-ones and (E)-N-hydroxybenzimidoyl chloride afforded novel polycyclic spiro[indoline-3,8'-isoxazolo[5,4-c]pyrrolo[2,1-a]isoquinolines] in good yields and with high diastereoselectivity. When 4-arylidenepyrazol-3-ones, 2-arylidene-1,3-indanediones and arylidenemalononitriles were employed in the reaction, the corresponding spiro[isoxazolo[5,4-c]pyrrolo[2,1-a]isoquinoline-8,4'-pyrazole], spiro[indene-2,8'-isoxazolo[5,4-c]pyrrolo[2,1-a]isoquinoline], and isoxazolo[5,4-c]pyrrolo[2,1-a]isoquinoline derivatives were also prepared in good yields and with high diastereoselectivty. The relative configurations of the polycyclic spiro compounds were clearly elucidated by determination of fifteen single crystal structures.

Tuning the redox potential of vitamin K3 derivatives by oxidative functionalization using a Ag(i)/GO catalyst

We propose herein initial results to develop optimum redox mediators by the combination of computational simulation and catalytic functionalization of the core structure of vitamin K₃. We aim to correlate the calculated energy value of the LUMO of different vitamin K₃ derivatives with their actual redox potential. For this, we optimized the catalytic alkylation of 1,4-naphthoquinones with a designed Ag(i)/GO catalyst and synthesized a series of molecules.

Nitrogen Oxides and Nitric Acid Enable the Sustainable Hydroxylation and Nitrohydroxylation of Benzenes under Visible Light Irradiation

A new type of waste recycling strategy is described in which nitrogen oxides or nitric acid are directly employed in photocatalyzed hydroxylations and nitrohydroxylations of benzenes. Through these transformations, otherwise costly denitrification can be combined with the synthesis of valuable compounds for various applications.

Tandem Double [3 + 2] Cycloaddition Reactions at Both C-1 and C-3 Atoms of N-Cyanomethylisoquinolinium Ylide

The base-promoted cycloaddition reaction of N-cyanomethylisoquinolinium chloride with 2-arylidene-1,3-indanediones in dry tetrahydrofuran resulted in the expected spiro[indene-2,1'-pyrrolo[2,1-a]isoquinoline] derivatives. However, the triethylamine-promoted three-component reaction of N-cyanomethylisoquinolinium chloride, aromatic aldehydes, and two molecules of 1,3-indanediones in acetonitrile afforded unique spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2'-indene] derivatives in satisfactory yields through tandem double [3 + 2] cycloaddition reactions.

Cobalt Ion Promoted Redox Cascade: A Route to Spiro Oxazine-Oxazepine Derivatives and a Dinuclear Cobalt(III) Complex of an N-(1,4-Naphthoquinone)-o-aminophenol Derivative

The study discloses that the redox activity of N-(1,4-naphthoquinone)-o-aminophenol derivatives (L^RH₂) containing a (phenol)-NH-(1,4-naphthoquinone) fragment is notably different from that of a (phenol)-NH-(phenol) precursor. The former is a platform for a redox cascade. L^RH₂ is redox noninnocent and exists in Cat-N-(1,4-naphthoquinone)(2-) (L^R 2-) and SQ-N-(1,4-naphthoquinone) (L^R •-) states in the complexes. Reactions of L^RH₂ with cobalt(II) salts in MeOH in air promote a cascade affording spiro oxazine-oxazepine derivatives (^OXL^R) in good yields, when R = H, Me, ^tBu. Spiro oxazine-oxazepine derivatives are bioactive, and such a molecule has so far not been isolated by a schematic route. In this context this cascade is significant. Dimerization of L^RH₂ → ^OXL^R in MeOH is a (6H⁺ + 6e) oxidation reaction and is composed of formations of four covalent bonds and 6-exo-trig and 7-endo-trig cyclization based on C-O coupling reactions, where MeOH is the source of a proton and the ester function. It was established that the active cascade precursor is [(L^Me •-)Co^IIICl₂] (A). Notably, formation of a spiro derivative was not detected in CH₃CN and the reaction ends up furnishing A. The route of the reaction is tunable by R, when R = NO₂, it is a (2e + 4H⁺) oxidation reaction affording a dinuclear L^R 2- complex of cobalt(III) of the type [(L^NO2 2-)₂Co^III₂(OMe)₂(H₂O)₂] (1) in good yields. No cascade occurs with zinc(II) ion even in MeOH and produces a L^Me •- complex of type [(L^Me •-)Zn^IICl₂] (2). The intermediate A and 2 exhibit strong EPR signals at g = 2.008 and 1.999, confrming the existence of L^Me •- coordinated to low-spin cobalt(III) and zinc(II) ions. The intermediates of L^RH₂ → ^OXL^R conversion were analyzed by ESI mass spectrometry. The molecular geometries of ^OXL^R and 1 were confirmed by X-ray crystallography, and the spectral features were elucidated by TD DFT calculations.

A Redox-Active Cascade Precursor: Isolation of a Zwitterionic Triphenylphosphonio-Hydrazyl Radical and an Indazolo-Indazole Derivative

A redox-active [ML] unit (M = Co^II and Mn^II; LH₂ = N'-(1,4-dioxo-1,4-dihydronaphthalen-2-yl)benzohydrazide) defined as a cascade precursor that undergoes a multicomponent redox reaction comprising of a C-N bond formation, tautomerization, oxidation, C-C coupling, demetalation, and affording 6,14-dibenzoylbenzo[f]benzo[5,6]indazolo[3a,3-c]indazole-5,8,13,16-tetraone (^IndL₂) is reported. Conversion of LH₂ → ^IndL₂ in air is overall a (6H⁺+6e) oxidation reaction, and it opens a route for the syntheses of bioactive diarylindazolo[3a,3-c]indazole derivatives. The reaction occurs via a radical coupling reaction, and the radical intermediate was isolated as a triphenylphosphonio adduct. In presence of PPh₃ the [ML] unit promotes a reaction that involves a C-P bond formation, tautomerization, and oxidation to yield a stable zwitterionic triphenylphosphonio-hydrazyl radical (^PPh3L^±•). Conversion of LH₂ → ^PPh3L^±• is a (3H⁺+3e) oxidation reaction. To authenticate the [ML] unit, in addition to the ^IndL₂, a zinc(II) complex, [(L₃)Zn^II(H₂O)Cl]·2MeOH (1·2MeOH), was successfully isolated (L₃H = a pyridazine derivative of 1,4 naphthoquinone) from a reaction of LH₂ with hydrated ZnCl₂. Conversion of 3LH₂ → 1 is also a multicomponent (6H⁺+6e) oxidation reaction promoted by zinc(II) ion via a radical intermediate. Facile oxidation of [L^2-] to [L^•-] that was considered as an intermediate of these conversions was confirmed by isolating a 1,4 naphthoquinone-benzhydrazyl radical (LH^•) complex, [(LH^•)Zn^II(H₂O)Cl₂] (2H^•). The intermediates of LH₂ → ^IndL₂, LH₂ → ^PPh3L^±•, and 3LH₂ → 1 conversions were analyzed by electrospray ionization mass spectroscopy. The molecular and electronic structures of ^PPh3L^±•, ^IndL₂, 1·2MeOH, and 2H^• were confirmed by single-crystal X-ray crystallography, electron paramagnetic resonance spectroscopy, and density functional theory calculations.

Formation of diverse polycyclic spirooxindoles via three-component reaction of isoquinolinium salts, isatins and malononitrile

The triethylamine promoted three-component reaction of N-(4-nitrobenzyl), N-ethoxycarbonylmethylisoquinolinium bromide, isatins and malononitrile in ethanol afforded spiro[indoline-3,2′-pyrrolo[2,1-a]isoquinolines] in good yields and with high diastereoselectivity. The similar reaction of N-cyanomethylisoquinolinium chloride mainly gave complex indolo[2″,3″:2′,3′]pyrrolo[3′,4′:4,5]pyrrolo[2,1-a]isoquinoline derivatives. However, the three-component reaction of N-cyanomethylisoquinolinium chloride, isatins and ethyl cyanoacetate mainly resulted in functionalized spiro[indoline-3,8′-pyrido[2′,3′:4,5]pyrrolo[2,1-a]isoquinolines].

Diastereoselective synthesis of benzo[d]chromeno[3′,4′:3,4]pyrrolo[2,1-b]thiazoles via cycloaddition reaction of benzothiazolium salts with 3-nitrochromenes

Diastereospecific synthesis of benzo[d]chromeno[3′,4′:3,4]pyrrolo[2,1-b]thiazoles via cycloaddition reaction of benzothiazolium salts with 3-nitrochromenes.

A [3 + 2]–[4 + 2]–[3 + 2] cycloaddition sequence of isoquinolinium ylide

A unique [3 + 2]–[4 + 2]–[3 + 2] cycloaddition sequence of isoquinolinium ylide is investigated to afford polycyclic compounds with ten stereogenic centers.

Chloroacetate Promotes and Participates in the Oxidative Annulation of Pyridines/Isoquinoline by Using Oxygen as the Oxidant

The aerobic oxidative annulation of chalcones, pyridines/isoquinoline and ethyl chloroacetate to indolizines was achieved by cascade reaction. Various functional groups on chalcones were tolerated. And different pyridines derivatives could also be suitable substrates. Ethyl chloroacetate is an essential component in participating of the oxidative annulation process. Overall, this protocol is very practical and efficient by using molecular oxygen as oxidant with high selectivity for the annulation product.

When Indolizine Meets Quinoline: Diversity-Oriented Synthesis of New Polyheterocycles and Their Optical Properties

Fluorescence-based technologies play a pivotal role in various biomedical applications. Here we report an efficient route to a new class of fluorophores, indolizino[3,2-c]quinolines, via the oxidative Pictet-Spengler cyclization strategy. The condensation of several 2-methylpyridines with 2-bromo-2'-nitroacetophenone allowed for the rapid assembly of indolizines with a 2-nitrophenyl group at the C2 position. The subsequent reduction of the nitro group under mild conditions followed by oxidative Pictet-Spengler cyclization with various aryl aldehydes in the presence of a catalytic amount of FeCl3 furnished the indolizino[3,2-c]quinolines in good overall yields. We also examined the photophysical properties of this new series of polyheterocyclic compounds. Several indolizino[3,2-c]quinolines were found to have unique and desirable optical properties, suggesting that these compounds may be suitable for use as prospective fluorescent probes in aqueous systems.

A one-pot three-component reaction involving 2-aminochromone in aqueous micellar medium: a green synthesis of hexahydrochromeno[2,3-b]quinolinedione

An efficient and green synthesis of hitherto unreported 11-(chromen-3-yl)-8,8-dimethyl-8,9-dihydro-6H-chromeno[2,3-b]quinoline-10,12(7H,11H)-dione has been accomplished by a three-component reaction involving 2-aminochromone, chromone-3-carbaldehyde, and 5,5-dimethyl-1,3-cyclohexanedione (dimedone) in 0.5 M aqueous SDS solution. The mechanism of the reaction has been studied by isolating the reaction intermediate. This methodology features eco-friendly reaction conditions, a simple working procedure, high atom-economy and high efficiency in product formation.

Efficient approach to 2-hydroxy-2,3-dihydrofuran derivatives and its application for the synthesis of novel 4-(1H-pyrazol-4-yl)pyridazines

A highly efficient method for the synthesis of 2-hydroxy-2,3-dihydrofuran derivatives from 1,4-enediones and phenacyl pyridinium halides via a domino reaction has been developed. At the same time, we also synthesize the novel 4-(1H-pyrazol-4-yl)pyridazine skeleton.

Copper(ii) bromide-catalyzed intramolecular decarboxylative functionalization to form a C(sp3)–O bond for the synthesis of furo[3,2-c]coumarins

Copper(ii) bromide-catalyzed intramolecular decarboxylative functionalization to form a C(sp³)–O bond has been developed.

Base-catalyzed synthesis of amides and imines via C–C and CC bond cleavage

A simple and efficient protocol has been developed for amides and imines synthesis from 1,3-dicarbonyls and α,β-unsaturated ketones respectively with N-arylureas in the presence of inexpensive and easily available KOH base under solvent free condition.

Copper(II)-catalyzed indolizines formation followed by dehydrogenative functionalization cascade to synthesize 1-bromoindolizines

A one-pot, three-component cascade reaction between pyridine, α-acylmethylbromide, and maleic anhydride leading to direct access of 1-bromoindolizines in high yields has been developed. This protocol is accomplished via a reaction sequence of 1,3-dipolar cycloaddition of the pyridinium ylide with maleic anhydride, oxidative decarboxylation of the primary cycloadduct, and dehydrogenative bromination of the resulting 1-unsubstituted indolizine. Copper chloride was used as a catalyst and oxygen as the terminal oxidant. This reaction represents the first example of transition-metal-catalyzed direct dehydrogenative bromination of indolizine at the C-1 position. Moreover, the obtained 1-bromoindolizines can be transformed to other 1-substituted indolizines such as 1-arylindolizines via a simple reaction process.

Copper(ii)-catalyzed cleavage of carbon–carbon triple bond to synthesize 1,2,3-triesterindolizines

An efficient Cu(ii)-catalyzed carbon–carbon triple bond cleavage protocol for the synthesis of 1,2,3-triesterindolizines via the reaction of pyridines with butynedioates has been developed.