An Efficient Approach for 3,3-Disubstituted Oxindoles Synthesis: Aryl Iodine Catalyzed Intramolecular C-N Bond Oxidative Cross-Coupling

Intermolecular α-Functionalization of Benzylamides with N-Nucleophiles via Oxidative Umpolung: Synthesis of Tetrasubstituted 3,3'-Oxindoles

A hypervalent iodine-mediated intermolecular α-umpolung reaction between α-aryl- or alkyl-substituted amides and benzotriazoles or purine derivatives as N-centered nucleophiles has been established. The reaction involves sequential intra/intermolecular oxidative C-N couplings in a controlled manner, affording tetrasubstituted 3,3'-oxindoles in moderate to good yields. This approach efficiently addresses the challenges in constructing tetrasubstituted carbon centers via α-umpolung functionalizations of carbonyl compounds and serves as a new strategy for synthesizing biologically important 3,3'-disubstituted oxindoles.

Expeditious entry into carbocyclic and heterocyclic spirooxindoles

Spirocyclic frameworks have attracted synthetic practitioners due to their unique three-dimensional assembly, improved metabolic stability, solubility, and increased molecular complexity with regard to planar architectures. A recent surge in the number of spirocyclic oxindoles inhibiting enzymes, moderating unique protein-protein interactions, modulating receptors and transporters is testament to their prevalence. Against this background, the construction of spirocyclic frameworks containing an oxindole moiety as a torsional switch via stereoselective methods is in great demand. Herein we present a summary of the past three years in the progress of metal, organic molecule, nanostructured particle mediated, and even uncatalyzed versions of the highly diastereo- and enantioselective pathways leading to oxindole spirocycles.

Construction of Benzimidazolone Derivatives via Aryl Iodide Catalyzed Intramolecular Oxidative C-H Amination

The first aryl iodide catalyzed intramolecular C-H amination of phenylurea has been disclosed for high-efficiency synthesis of benzimidazolone derivatives in excellent yields (up to 97%) by an operationally simple one-step organocatalytic oxidative process. Fluorinated protic alcohols can efficiently accelerate the conversion of this transformation. The straightforward method has good functional group tolerance and can be performed with an inexpensive and readily accessible catalyst with high proficiency.

Visible light-mediated radical-cascade addition/cyclization of arylacrylamides with aldehydes to form quaternary oxindoles at room temperature

The visible light-induced oxidative radical cascade coupling of N-arylacrylamides with aldehydes using bromide as the hydrogen atom transfer agent to synthesize functional oxindoles is described.

μ-Oxo-Hypervalent-Iodine-Catalyzed Oxidative C-H Amination for Synthesis of Benzolactam Derivatives

Benzolactams have unique biological activity and high utility in the synthesis of valuable compounds with direct applicability to oxindole alkaloids and antibacterial agents. Despite recent advances in organic chemistry and the growing number of reported methods for synthesizing benzolactams, their preparation still requires a multistep process. C-H amination reactions can convert aromatic C(sp²)-H bonds directly to C(sp²)-N bonds, and this direct approach to C-N bond formation offers effective access to benzolactams. Hypervalent iodine reagents are promising tools for achieving oxidative C-H amination. Motivated by our ongoing research efforts toward the development of useful hypervalent-iodine-mediated oxidative transformations, we herein describe an effective intramolecular oxidative C-H amination reaction based on μ-oxo hypervalent iodine catalysis for the synthesis of benzolactams bearing various functional groups.