Synthesis of Functionalized 6-Hydroxy-2-oxindole Derivatives by Phenoxide Cyclization

Intramolecular cyclization of N-aryl amides for the synthesis of 3-amino oxindoles

A mild and efficient strategy to synthesize pharmaceutically important 3-amino oxindoles from readily available N-aryl amides has been developed. This unique reaction proceeds via the intramolecular cyclization of 2-azaallyl anions with N-aryl amides to afford 3-amino substituted oxindoles. This novel method avoids the direct usage of transition metal catalysts and additional oxidants. Furthermore, the anti-pulmonary fibrosis activity evaluation showed that 3-amino oxindole 2f significantly inhibited collagen deposition, which can ameliorate pulmonary fibrosis by reducing excessive extracellular matrix (ECM) deposition.

Synthesis of 3-substituted 2-oxindoles from secondary α-bromo-propionanilides via palladium-catalyzed intramolecular cyclization

In contrast to aromatic halides, coupling reactions involving oxidative addition of alkyl halides, especially secondary or tertiary halides, to transition metals tend to be more challenging. Herein a palladium-catalyzed intramolecular cyclization of α-bromo-propionanilides has been developed, delivering a series of 3-substituted 2-oxindoles in high yields. The method features easy to prepare starting materials, broad substrate scope and excellent functional group tolerance. A detailed mechanistic investigation has been performed.

Rapid Access to Benzimidazo[1,2-a]quinoline-Fused Isoxazoles via Pd(II)-Catalyzed Intramolecular Cross Dehydrogenative Coupling: Synthetic Versatility and Photophysical Studies

An efficient and atom-economical palladium-catalyzed intramolecular cross dehydrogenative coupling (CDC) reaction has been developed for the construction of highly π-conjugated benzimidazo[1,2-a]quinoline-fused isoxazole scaffolds using molecular oxygen as sole oxidant. The approach portrayed wide substrate scope with good functional group tolerance and depicted a useful tool for the generation of fluorescence active compounds with high quantum yield. Synthetic versatility of the method via Fe-catalyzed reductive isoxazole ring cleavage toward pyridine, pyrimidine, pyrazole fused heteropolycyclic compounds has been showcase.

Stereoselective three-component cascade synthesis of α-substituted 2,4-dienamides from gem-difluorochloro ethanes

Herein, we describe a new transition metal-free Claisen rearrangement for the synthesis of α-substituted 2,4-dienamides. The one-pot, stereoselective three-component cascade reaction between a series of propargyl alcohols, amines, and gem-difluorochloro ethane derivatives afforded various polysubstituted 2,4-dienamides in good yields. This synthetic method for 1,1-captodative dienes, α-substituted 2,4-dienamides, can be utilized for preparing pharmaceutical analogues containing an indolin-2-one or lactone moiety.

When Ethyl Isocyanoacetate Meets Isatins: A 1,3-Dipolar/Inverse 1,3-Dipolar/Olefination Reaction for Access to 3-Ylideneoxindoles

A new CuI/1,10-phen-catalyzed reaction for the synthesis of 3-ylideneoxindoles from readily available isatins and ethyl isocyanoacetate, in which ethyl isocyanoacetate acts as a latent two-carbon donor like the Wittig reagent, is reported. A tandem procedure including 1,3-dipolar cycloaddition/inverse 1,3-dipolar ring opening/olefination allows the preparation of 3-ylideneoxindoles with broad functional group tolerance.

K2CO3-Mediated Cyclization and Rearrangement of γ,δ-Alkynyl Oximes To Form Pyridols

A novel K₂CO₃-mediated cyclization and rearrangement of γ,δ-alkynyl oximes for the synthesis of pyridols is described. The process accomplishes an efficient [1,3] rearrangement of the O-vinyl oxime intermediate which is in situ generated from the intramolecular nucleophilic addition of γ,δ-alkynyl oximes. The reaction employs readily accessible starting materials, tolerates a wide range of functional groups, and gives a variety of synthetically challenging pyridols in good yields.