Gold-Catalysed Nitroalkyne Cycloisomerization - Synthetic Utility

Gold-Catalyzed Oxidation Reactions of Thioalkynes with Quinoline N-Oxides: A DFT Study

Mechanistic investigation of the gold-catalyzed oxidative reactions of thioalkynes with quinoline N-oxides was performed using density functional theory (DFT) calculations. For the oxidative rearrangement of thioalkynes with quinoline N-oxide to yield the same products, the Cβ-oxidation of thioalkynes was predicted to be competitive with Cα-oxidation, with the Cβ-oxidative process slightly more favorable. However, for the oxidative alkenylation of propargyl aryl thioethers with quinoline N-oxides, the Cβ-oxidation of thioether by quinoline N-oxide generated the product 3-hydroxy-1-alkylidene phenylthiopropan-2-one. Moreover, the ring opening of the four-membered sulfonium intermediate was achieved by the nucleophilic attack of quinoline N-oxide rather than a water molecule.

Synthesis, characterization, and crystal structure of 2-(2-azido-phen-yl)-3-oxo-3H-indole 1-oxide

An attempt to explore the reactivity of the nitro group in the presence of gold catalysis in comparison to the azide group yielded intriguing results. Surprisingly, only the nitro group exhibited reactivity, ultimately giving rise to the formation of the title isatogen, C14H8N4O2. In the crystal structure, weak C-H⋯O hydrogen bonds and π-π stacking inter-actions link the mol-ecules. The structure exhibits disorder of the mol-ecule.

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.

Synthesis of Hydroxysuccinimide Substituted Indolin-3-ones via One-Pot Cascade Reaction of o-Alkynylnitrobenzenes with Maleimides under Au(III)-Cu(II) Relay/Synergetic Catalysis

Presented herein is a one-pot cascade reaction of o-alkynylnitrobenzenes with maleimides leading to the formation of hydroxysuccinimide substituted indolin-3-ones under Au(III)-Cu(II) relay/synergetic catalysis. Mechanistically, the formation of the title products involves an unprecedented cascade process including (1) nitro-alkyne cycloisomerization of o-alkynylnitrobenzene to give isatogen; (2) [3 + 2] dipolar cycloaddition of isatogen with maleimide; and (3) ring opening of the in situ formed isoxazolidine moiety under neutral conditions. Notably, a wide range of substrates bearing various functional groups are compatible with the reaction conditions to give a series of highly valuable hybrid compounds in good efficiency with excellent atom economy. In addition, the products thus obtained could be easily transformed into the corresponding maleimide substituted indolin-3-ones. Importantly, some products demonstrated significant antiproliferative activity in human cancer cell lines.

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

Herein we present a transition-metal-free cross-coupling reaction of isatogens with boronic acids through a 1,4-metalate shift of a boron "ate" complex. This coupling reaction provides a feasible method to deliver valuable 2,2-disubstituted indolin-3-one derivatives with excellent regioselectivity, which exhibit operational simplicity, good functional group tolerance, and a broad substrate scope.