Rh(III)-Catalyzed Spiroannulation Reaction of N-Aryl Nitrones with 2-Diazo-1,3-indandiones: Synthesis of Spirocyclic Indole-N-oxides and Their 1,3-Dipolar Cycloaddition with Maleimides

Abstract

An efficient strategy for the preparation of spirocyclic indole-N-oxide compounds through a Rh(III)-catalyzed [4 + 1] spiroannulation reaction of N-aryl nitrones with 2-diazo-1,3-indandiones as C1 synthons under extremely mild conditions is presented. From this reaction, 40 spirocyclic indole-N-oxides were easily obtained in up to 98% yield. In addition, the title compounds could be successfully used for the construction of structurally intriguing maleimide-containing fused polycyclic scaffolds via a diastereoselective 1,3-dipolar cycloaddition reaction with maleimides.

Gold-catalyzed intermolecular tandem cyclization/[4 + 3] cycloaddition of 2-(1-alkynyl)-cyclopropyl pyridines with nitrones: an efficient strategy for the synthesis of [1,2]oxazepino[5,4-a] indolizines

“…9 Given the importance of this structural class, the development of synthetic methods that would lead to more complex indolizines is of great significance, and the introduction of fused rings could be used to access compounds with molecular complexity. Herein, we report a general and efficient method for the synthesis of seven-membered heterocycle-fused indolizine scaffolds from 2-(1-alkynyl-cyclopropyl)pyridines 7 b and nitrones 10 under the catalysis of PPh 3 AuNTf 2 .…”