Tandem Synthesis of Pyrrolo[2,3-b]quinolones via Cadogen-Type Reaction

Base-Promoted and Copper(I)-Catalyzed Tandem Cyclization-C(sp2)-N Coupling of Vinyl Malononitriles with Ortho-Nitrochalcones: Access to Acridones and their Fused Derivatives

An efficient Cs2CO3-promoted and copper(I)-catalyzed double cyclization of ortho-nitrochalcones with vinyl malononitriles for the de novo access to a variety of tri- and tetra-substituted acridones and their fused derivatives with a value-added CN group has been developed for the first time. This one-pot operation proceeds through a Michael-cyclization-aromatization, followed by regioselective ipso-amination via nucleophilic aromatic substitution (SNAr) reaction, resulting in two C═C bonds and a C-N bond for acridone ring synthesis. This economic strategy based on 100% carbon atoms ensures the successive formation of two rings in a one-pot operation, good to high yields, a wide range of substrates, and good tolerance of functionalities. In addition, acridones were converted into several value-added acridones and acridines, highlighting the synthetic versatility and usefulness of the prepared acridone derivatives.

Copper/Zinc-Catalyzed Stitching of 2-Carbonylanilines with Bis(ynamides): Access to Pyrrolo[2,3-b]quinolines and Its Photophysical Studies

Herein, a one-pot desulfonylative protocol enabled by copper(II)/zinc(II) salts to access pyrrolo[2,3-b]quinolines in good to excellent yields from 2-carbonylanilines and ynamide-derived buta-1,3-diynes has been reported. Significantly, various 2-carbonylanilines carrying reactive functional groups are well tolerated. Moreover, a gram-scale synthesis and synthetic application highlight the practical utility of the current protocol. Notably, the fluorescence properties of pyrrolo[2,3-b]quinolines have been recorded, and their potential use as a fluorescent probe in the imaging of live cells has been demonstrated.

Synthesis, Nematicidal Evaluation, and the Structure-Activity Relationship Study of Aurone Derivatives

Plant-parasitic nematodes (PPNs) are one of the major threats to modern agriculture. Chemical nematicides are still required for the management of PPNs. Based on our previous work, the structure of aurone analogues was obtained using a hybrid 3D similarity calculation method (SHAFTS, SHApe-FeaTure Similarity). Thirty-seven compounds were synthesized. The nematicidal activity of target compounds against Meloidogyne incognita (root-knot nematode, M. incognita) was evaluated, and the structure-activity relationship of synthesized compounds was analyzed. The results showed that compound 6 and some of its derivatives exhibited impressive nematicidal activity. Among these compounds, compound 32 bearing 6-F showed the best in vitro and in vivo nematicidal activity. Its lethal concentration 50% after exposure to 72 h (LC_50/72 h) value was 1.75 mg/L, and the inhibition rate reached 97.93% in the sand at 40 mg/L. At the same time, compound 32 also exhibited excellent inhibition on egg hatching and moderate inhibition on the motility of Caenorhabditis elegans (C. elegans).

Synthesis of 2-carboxyaniline-substituted maleimides from 2'-nitrochalcones

A practical, one-pot approach to 3-anilino-4-(het)arylmaleimides by simple heating of aqueous DMSO solution of 2'-nitrochalcones with potassium cyanide in the presence of formic acid has been developed. This new reaction provides effective access to a variety of β-substituted α-aminomaleimides which have recently become a subject of growing interest as small, easily modified and environmentally responsive fluorescent probes.

Nitroarenes and nitroalkenes as potential amino sources for the synthesis of N-heterocycles

Nitro-compounds are one of the cheapest and most readily available materials in the chemical industry and are commonly utilized as versatile building blocks. Previously, the synthesis of N-heterocycles was largely based on anilines. The utilization of nitroarenes and nitroalkenes for the synthesis of N-heterocyclic compounds can save at least one step, however, as compared to anilines. Thus, considerable attention has been paid to nitroarenes and nitroalkenes as new potential amino sources. Significant progress has been made in the reductive cyclization of nitroarenes or nitroalkenes to access various N-heterocycles in recent years. Herein, we comprehensively summarize the recent progress in the construction of N-heterocycles using nitroarenes and nitroalkenes as potential amino sources. The compatibility of the reaction substrate, its mechanism, applications, advantages, and limitations in this field are also discussed in detail.

Recent Advances to Mediate Reductive Processes of Nitroarenes Using Single-Electron Transfer, Organomagnesium, or Organozinc Reagents

Recent advances in the development of reductive reactions of nitroarenes using organomagnesium-, organozinc-, and single electron transfer reagents is discussed within this review. The review is divided into the following sections: IntroductionOrganomagnesium-mediated reductive reactionsOrganozinc- and zinc-mediated reductive reactionsIodine-catalyzed redox cyclizationsTitanium(III)-mediated reductive cyclizationsSulfur-mediated reductive reactionsAlkoxide-mediated reductive reactions4,4'-Bipyridine-mediated reductive reactionsVisible light-driven reductive amination reactionsElectrochemical reductive reactionsConclusion.

Cu(I)-Catalyzed and Base-Promoted [5 + 2 + 1] Cascade Cyclization of 2-Nitrochalcones with Aliphatic Primary Amines to 5H-Pyrimido[5,4-b]indole Frameworks

An unprecedented [5 + 2 + 1] cascade cyclization to the preparation of 5H-pyrimido[5,4-b]indole derivatives has been disclosed. The novel protocol of 2-nitrochalcones reacted with aliphatic primary amines catalyzed by CuI and promoted by Cs₂CO₃, which underwent a critical intermediate 2,3-disubstituted indole, providing structurally diverse 5H-pyrimido[5,4-b]indoles in generally high yields (77-90%) and broad substrate scopes (34 examples).

One-Pot Synthesis of (E)-2-(3-Oxoindolin-2-ylidene)-2-arylacetonitriles

A highly efficient and expeditious one-pot approach towards 2-(3-oxoindolin-2-yl)acetonitriles was designed, which involves a base-assisted aldol reaction of ortho-nitroacetophenones, followed by hydrocyanation, triggering an unusual reductive cyclization reaction.

Recent Advances in the Transition Metal-Free Synthesis of Heterocycles from α, β-Unsaturated Ketones

Heterocyclic compounds are an inevitable part of our life. These important classes of molecules have a wide range of applications starting from life-sustaining drugs to agrochemicals. Numerous methods, including metal...

Cu/base co-catalyzed [3+3] cycloaddition for the synthesis of highly functionalized 4-fluoropyridines

An efficient, straightforward and general method for the de novo synthesis of highly functionalized 4-fluoropyridines was developed via a cooperative copper- and base-catalyzed [3+3] cycloaddition of active methylene isocyanides with difluorocyclopropenes. The resulting 4-fluoropyridines can be readily diversified by various nucleophiles.

N2H4-H2O Enabled Umpolung Cyclization of o-Nitro Chalcones for the Construction of Quinoline N-Oxides

Umpolung is a unique strategy which converts the property of an atom into the opposite one. An efficient and general method for the construction of quinoline N-oxides via umpolung of carbonyl groups was developed from ortho-nitro chalcones and hydrazine in basic conditions. The strategy is transition-metal free and has good functional group tolerance, environmental friendliness, as well as mild reaction conditions with nitrogen gas as the byproduct.

Synthesis of Sulfamate-Fused 2-Aminopyrroles via an Isocyanide-Based Three Component [1+2+2] Annulation

An efficient preparation of sulfamate-fused 2-aminopyrroles was achieved through an isocyanide-based three-component [1+2+2] annulation of isocyanides, dialkyl acetylenedicarboxylates, and sulfamate-derived cyclic imines in good to excellent yields (up to 99 %). This reaction proceeds smoothly without any activation or modification of substances under neutral and metal-free conditions. The reaction could also be conveniently performed on a gram scale.

A catalyst-free aqueous mediated multicomponent reaction of isocyanide: expeditious synthesis of polyfunctionalized cyclo[b]fused mono-, di- and tricarbazoles

A new multi-component reaction is developed for the synthesis of cyclo[b]fused mono-, di- and tricarbazoles from o-alkenyl arylisocyanides, aldehydes, and cyclic diketones in ethanol/water (1 : 1) as the solvent system.

Unexpected cyclization of ortho-nitrochalcones into 2-alkylideneindolin-3-ones

An original, facile, and highly efficient method for the preparation of 2-(3-oxoindolin-2-ylidene)acetonitriles from ortho-nitrochalcones is described. The featured transformation is a triggered Michael addition of the cyanide anion to the chalcone followed by a cascade cyclization mechanistically related to the Baeyer–Drewson reaction.

Highly efficient cascade involving Michael addition and Baeyer–Drewson reaction is triggered by cyanide anion and transforms ortho-nitrochalcones into 2-(3-oxoindolin-2-ylidene)acetonitriles.

Domino synthesis of fully substituted pyridines by silver-catalyzed chemoselective hetero-dimerization of isocyanides

A silver-catalyzed hetero-dimerization of various vinyl isocyanides with isocyanoacetamides has been developed for the efficient and practical synthesis of fully substituted pyridines in a single operation.

Synthesis of Benzothiophene-Fused Oxa[6.6.5]tricyclic Skeletons through a Cinchonidine- or NaOH-Promoted Quadruple Domino Sequence

Two base-promoted quadruple domino reactions between thioaurones and allylic phosphonium salts have been developed to synthesize benzothiophene-fused oxa[6.6.5]tricyclic skeletons in moderate to good yields with excellent stereoselectivity and broad functional-group tolerance. This is a simple and useful protocol for the rapid construction of the umbrella-like oxa[6.6.5]tricyclic skeleton.

[1 + 2 + 3] Annulation as a General Access to Indolo[3,2- b]carbazoles: Synthesis of Malasseziazole C

A formal [1 + 2 + 3] annulation of methyleneindolinones with o-alkenyl arylisocyanides has been developed for the general and efficient synthesis of both symmetrical and unsymmetrical indolo[3,2- b]carbazoles. The chemoselectivity of this domino reaction was tuned by a tethered alkenyl group, which enables successive formation of three new bonds and two rings from readily accessible starting materials in a single operation. Furthermore, this methodology was used as a key step in the synthesis of the alkaloid malasseziazole C.

Formal [1 + 2 + 3] Annulation: Domino Access to Carbazoles and Indolocarbazole Alkaloids

A new formal [1 + 2 + 3] annulation of o-alkenyl arylisocyanides with α, β-unsaturated ketones under metal-, base-, and acid-free conditions is disclosed. This domino reaction provides a general protocol for the efficient and practical synthesis of a wide range of carbazole derivatives from readily available starting materials in a single operation. Furthermore, this methodology was used as the key step in a protecting-group-free synthesis of indolocarbazole alkaloids arcyriaflavin A and racemosin B.

Transition-metal-free synthesis of polysubstituted pyrrole derivatives via cyclization of methyl isocyanoacetate with aurone analogues

A transition-metal-free, operationally simple and atom-economic protocol that converts isocyanoacetates and aurones to 2,3,4-trisubstituted pyrroles catalyzed by NaOH was presented.