Regioselective Cross-Coupling of Isatogens with Boronic Acids to Construct 2,2-Disubstituted Indolin-3-one Derivatives

Intercepting an avoided α-iminol rearrangement with a Petasis reaction for the synthesis of 2,3-diaryl substituted indoles

Rearrangement reactions are generally considered to be a rapid and synergistic intramolecular reconstructing process that is insensitive to intermolecular intruders. We report that α-iminol rearrangements could be strategically redirected by the interception of Petasis reactions, in the context of being avoided by strong electron-withdrawing groups on the migrative aryl units. 1,4-Aryl migration prevails over 1,2-aryl migration via forming a boron-ate complex. By leveraging this reactivity, we developed a regiospecific synthesis of unsymmetrically 2,3-diaryl substituted indoles from three readily available feedstocks: an amine, an arylglyoxal, and a boronic acid. While traditional Petasis reactions with similar three-component inputs are typically applied to build C(sp3)-C(sp2) and C(sp3)-C(sp3) bonds, the present transformation offers a special opportunity for constructing a C(sp2)-C(sp2) linkage. Highly substituted indole motifs with structural diversity in the C2 position are easily accessed by this three-component reaction. A mechanism containing a copper-cobalt collaborative promotion process was suggested.

Strategic 1,n-migration of boronate complexes: a novel platform for remote C-C bond construction

Organoboron compounds play a pivotal role in diverse scientific disciplines, including chemistry, materials science, energy research, and medicinal chemistry. In recent years, research efforts have predominantly focused on 1,2-metallate migrations of tetracoordinate boronate complexes, while remote migrations, particularly 1,n-metallate migrations (n > 2), remain challenging due to their inherent complexity. This comprehensive review systematically examines seminal contributions to the field of 1,n-metallate migration reactions (n > 2). Our critical analysis reveals that progress in this domain has been fundamentally driven by the strategic design and synthesis of novel tetracoordinate boron complexes, with a notable evolution from conventional O-B coordination motifs to more sophisticated C-B-bonded architectures. Recent methodological advancements have further expanded the structural diversity and mechanistic understanding of these transformations. Although the number of reported cases remains limited and the research landscape is somewhat fragmented, the existing systems underscore the significance of these migration reactions, drawing considerable attention to this area and inspiring further exploration.

Bi(OTf)3-Catalyzed Cascade Cycloaddition-Decarbonylation-N-Deoxygenative Aromatization between 2-Arylisatogens and Styrenes: Unveiling a Synthesis of 2,4-Diarylquinolines

An unprecedented Bi(OTf)3-catalyzed reaction between 2-arylisatogens and vinylarenes to yield 2,4-diarylquinolines is reported. The transformation occurred via a BiIII-coordination to the embedded anionic nitrone oxygen, which induced a regiospecific stepwise formal [4 + 2]-cycloaddition with vinylarenes to yield a strained tricyclic intermediate, which subsequently extruded gaseous carbon monoxide. N-Deoxygenative aromatization ensued to produce 2,4-diarylquinolines. The protocol was applicable to a variety of substrates to produce the quinolines in up to an 89% yield.

Isatogenols as Precursors for the Synthesis of Fully Substituted Indolines through Regio- and Stereoselective [3 + 2] Cycloaddition Using Various Olefins

Here, we describe a unique reactivity of isatogen derivatives bearing a hydroxy group at the C3-position (isatogenol) and their synthetic application to highly regio- and stereoselective [3 + 2] cycloaddition reactions. This method provides facile access to polyfused and highly functionalized heterocycles including consecutive stereocenters. Furthermore, DFT calculations revealed that hydrogen bonding is a key to controlling the regio- and stereoselectivity in the cycloaddition using acrylates.

Boron-catalysed transition-metal-free arylation and alkenylation of allylic alcohols with boronic acids

The development of efficient catalytic reactions with excellent atom and step economy employing sustainable catalysts is highly sought-after in chemical synthesis to reduce the negative effects on the environment. The most commonly-used strategy to construct allylic compounds relies on the transition-metal-catalysed nucleophilic substitution reaction of allylic alcohol derivatives. These syntheses exhibit good yield and selectivity, albeit at the expense of toxic and expensive catalysts and extra steps. In this paper, we report a transition-metal-free arylation and alkenylation reaction between unprotected allylic alcohols and boronic acids. The reactions were performed with B(C₆F₅)₃ as the catalyst in toluene, and corresponding products were obtained in 23-92% yields. The reaction has mild conditions, scalability, excellent atom and step economy.

Low-Valent Tungsten-Catalyzed Controllable Oxidative Dehydrogenative Coupling of Anilines

Herein, we have developed an efficient tungsten-catalyzed homogeneous system for oxidative dehydrogenative coupling of anilines to selectively produce various azoaromatics and azoxyaromatics as well as 2-substituted indolone N-oxides by simply regulating the reaction solvent with peroxide as a terminal oxidant under additive-free conditions. These findings provide an experimental framework for exploring tungsten catalysis in organic synthesis and offer an efficient and convenient tactic for the selective oxidation of anilines.

Dearomative oxyphosphorylation of indoles enables facile access to 2,2-disubstituted indolin-3-ones

A highly efficient oxidative dearomatization of indoles with H-phosphorus oxides in the presence of TEMPO oxoammonium salt has been demonstrated. Through the intramolecular oxidative dearomatization of indoles and subsequent intermolecular nucleophilic addition with phosphorus nucleophile, a variety of structurally diverse arylphosphoryl and alkylphosphoryl indolin-3-ones were obtained in good yields with a broad substrate scope and high functional-group compatibility.