Transition-Metal-Free Aminoacylation of Ynones with Amides: Synthesis of 3-Carbonyl-4-quinolinones or Functionalized Enaminones

Catalyst-free reactions of anilines with β-chloroenones: synthesis of α-chloroenaminones and 1,4-benzodiazepines

The Michael addition of anilines to β-chloroenones gives enaminones by the elimination of hydrochloric acid (HCl). These enaminones are transformed into α-chloroenaminones via in situ sp2 C-H functionalization. Anilines that are attached to an electron-donating group react more readily with β-chloroenone to give the corresponding products in excellent yields. A highly atom-economical method has been developed using dimethyl sulfoxide (DMSO) as a green oxidant and solvent. The desired α-functionalized enaminones are formed in good yields with excellent Z-selectivity. We have established the generality of this reaction with many substrates, and scaled-up reactions have been performed to showcase the practical applications. A catalyst-free double annulation of β-chloroenones with o-phenylenediamine has also been demonstrated for the synthesis of 1,4-benzodiazepine derivatives in moderate yields under mild reaction conditions.

Rhodium(III)-Catalyzed Coupling of Quinolin-8-carboxaldehydes with CF3-Imidoyl Sulfoxonium Ylides by Chelation-Assisted C(sp2)-H Bond Activation for the Synthesis of Trifluoromethyl-Substituted Enaminones

A rhodium(III)-catalyzed aldehydic C(sp2)-H imidoylmethylation of quinolin-8-carboxaldehydes with CF3-imidoyl sulfoxonium ylides (TFISYs) has been developed for the generation of α-imino ketones, which could be readily tautomerized to enaminones in moderate to excellent yields. In the transformation, TFISYs act as a kind of masked alkenylating reagents for the aldehyde moiety, and the obtained CF3-enaminone products have been successfully converted into other useful trifluoromethyl-substituted heterocycles.

15.4.5 Quinolinones and Related Systems (Update 2022)

Quinolinones, of which the quinolin-4(1H)-one ring system can be highlighted, represent an exciting class of nitrogen heterocycles. The quinolinone motif can be found in many natural compounds and approved drugs for several diseases. This chapter is a comprehensive survey of the methods for the synthesis of quinolin-2(1H)-ones, quinolin-4(1H)-ones, and their thio- and amino derivatives, and is an update to the previous Science of Synthesis chapter (Section 15.4), covering the period between 2003 and 2020.

Cascade C–N bond cleavage of amides/intramolecular amination reactions: an atom economical way to α-cabolin-4-ones

A novel one-pot procedure for the synthesis of 2,3-disubstituted α-carbolin-4-ones through successive C–N bond cleavage and intramolecular amination reactions involving a 1,2-acyl migration has been developed.

Selective Synthesis of Pyrano[3,2-b]indoles or Cyclopenta[b]indoles Tethered with Medium-Sized Rings via Cascade C-C σ-Bond Cleavage and C-H Functionalization

Highly atom-economical tandem reactions have been developed for the synthesis of pyrano[3,2-b]indoles or cyclopenta[b]indoles tethered with 7-, 8-, or 9-membered rings. These reactions first undergo a carbon-carbon σ-bond cleavage reaction of cyclic β-ketoesters. Next, in the presence of CuCl₂ and Ag₂CO₃, intramolecular O-H/C-H coupling occurs to give pyrano[3,2-b]indoles. This is the first example for capture of the enoloxyl radical of the intramolecular C-O bond formation reaction, whereas C3 nucleophilic addition afforded cyclopenta[b]indoles using TsOH·H₂O.

A Cascade Reaction of Michael Addition and Truce-Smiles Rearrangement to Synthesize Trisubstituted 4-Quinolone Derivatives

A novel transition-metal-free cascade reaction to synthesize 4-quinolone derivatives has been demonstrated. Michael addition and Truce-Smiles rearrangement are included in this protocol, providing a broad scope of 4-quinolones in moderate-to-excellent yields. This work serves as an example of the use of sulfonamides through Truce-Smiles rearrangement to build heterocyclic compounds under mild conditions.

Gold(iii)-catalyzed azide-yne cyclization/O-H insertion cascade reaction for the expeditious construction of 3-alkoxy-4-quinolinone frameworks

A gold-catalyzed 6-endo-dig azide-yne cyclization/O-H insertion cascade reaction of azide-tethered alkynes with alcohols has been developed, and it provides an expeditious access to 3-alkoxy-4-quinoline derivatives in good to high yields under mild and neutral reaction conditions with broad substrate generality. The utility of this method is emphasized by a scalable experiment and concise total synthesis of a bioactive natural product Leiokinine A, and other bioactive quinoline analogs.

Access to 2-Alkyl/Aryl-4-(1H)-Quinolones via Orthogonal "NH3" Insertion into o-Haloaryl Ynones: Total Synthesis of Bioactive Pseudanes, Graveoline, Graveolinine, and Waltherione F

An efficient one-pot synthesis of 4-(1H)-quinolones through an orthogonal engagement of diverse o-haloaryl ynones with ammonia in the presence of Cu(I), involving tandem Michael addition and ArCsp₂-N coupling, is presented. The substrate scope of this convenient protocol, wherein ammonium carbonate acts as both an in situ ammonia source and a base toward diverse 2-substituted 4-(1H)-quinolones, has been mapped and its efficacy validated through concise total synthesis of bioactive natural products pseudanes (IV, VII, VIII, and XII), graveoline, graveolinine, and waltherione F.

Cu-Catalyzed one-pot synthesis of thiochromeno-quinolinone and thiochromeno-thioflavone via oxidative double hetero Michael addition using in situ generated nucleophiles

A copper catalyzed three-component synthesis of π-conjugated tetracyclic thiochromeno-quinolinone and thiochromeno-thioflavone was established via oxidative double hetero Michael addition using in situ generated nucleophiles.

Synthesis of cyano-substituted carbazoles via successive C-C/C-H cleavage

A highly efficient protocol for the synthesis of polysubstituted cyano carbazoles has been developed. This process is realized through the tandem reactions of Cs2CO3 promoted C-C σ-bond activation of α-cyano ketones followed by Fe-catalyzed selective C-H and/or C-C bond activations. Two of the sp2 C-H bonds are functionalized, and two of the C-C σ-bonds are cleaved involving a 1,2-acyl migration during the reaction process.

Recent Advances in the Addition of Amide/Sulfonamide Bonds to Alkynes

The addition of amide/sulfonamide bonds to alkynes is not only one of the most important strategies for the direct functionalization of carbon⁻carbon triple bonds, but also a powerful tool for the downstream transformations of amides/sulfonamides. The present review provides a comprehensive summary of amide/sulfonamide bond addition to alkynes, including direct and metal-free aminoacylation, based-promoted aminoacylation, transition-metal-catalyzed aminoacylation, organocatalytic aminoacylation and transition-metal-catalyzed aminosulfonylation of alkynes up to December 2018. The reaction conditions, regio- and stereoselectivities, and mechanisms are discussed and summarized in detail.

Theoretical investigation on the mechanism of Cu(ii)-catalyzed synthesis of 4-quinolones: effects of additives HOTf vs. HOTs

Hydrogen-bond donor/proton-donor ability is revealed to be the primary factor that controls the catalytic capability of additives (HOTf vs. HOTs).

Rhodium(iii)-catalyzed [3 + 3] annulation reactions of N-nitrosoanilines and cyclopropenones: an approach to functionalized 4-quinolones

We report Rh(iii)-catalyzed [3 + 3] annulation reactions for the preparation of functionalized 4-quinolones from available N-nitrosoanilines and cyclopropenones.

Transition-metal-free C–C σ-bond activation of α-aryl ketones and subsequent Zn-catalyzed intramolecular cyclization: synthesis of tetrasubstituted furans

Atom-economical synthesis of tetrasubstituted furans from α-aryl ketones and alkynones through base-promoted cleavage of unstrained C–C single bonds of ketones and subsequent Zn-catalyzed cyclization.

An efficient tandem synthesis of chromones from o-bromoaryl ynones and benzaldehyde oxime

A transition-metal-free approach was developed to synthesize chromones from o-bromoaryl ynones and benzaldehyde oxime by sequential C–O bond formation.