Construction of Spiropyrroloindolines by Dearomative [3+2]-Cycloaddition of Indoles with Oxindole-Embedded Azaoxyallyl ­Cations

Abstract

Herein, [3+2] dearomative indole cycloaddition reaction with oxindole embedded azaoxyallyl cation at C3 is developed. Use of this new class of azaoxyallyl cation species in the reaction enables the access to more elaborate hexahydropyrrolo[2,3-b]indole moieties that contain a spiro-oxindole ring. The transformation highlights good substrate scope and good regio- and stereoselectivity for cycloaddition step. Several observations suggested that this class of azaoxyallyl cation can display different reactivity pattern from the commonly employed azaoxyallyl cation systems in the relevant literature.