Synthesis of 3-Hydroxyfluorenones Based on the Cascade Reaction of Aryl Enaminones with Benzyl Substituted Cyclopropanols

Abstract

Presented herein is a novel synthesis of 3-hydroxyfluorenones through the cascade reaction of aryl enaminones with benzyl substituted cyclopropanols. The formation of product is initiated by the introduction of an enone moiety onto aryl enaminone with cyclopropanol as a homoenolate precursor through aryl C−H bond activation, followed by intramolecular enamine Michael addition, enol Michael addition, amine elimination and aromatization-driven oxidative dehydrogenation. To our knowledge, this should be the first example for the specific synthesis of 3-hydroxyfluorenone derivatives via simultaneous formation of both indenone and phenol scaffolds through cascade C−H/C−C/C−N bond activation and three C−C bond formation. In general, this newly developed protocol features easily accessible substrates, synthetically and pharmaceutically valuable products, unique reaction pathway, good compatibility with various functional groups and ready scalability.

Keywords

3-Hydroxyfluorenones / Cascade reaction / Aryl enaminones / Benzyl substituted cyclopropanols / C−H activation / Synthetic methods / Step-economy / Carbocycles / Annulation

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2025 SIOC, CAS, Shanghai, & WILEY-VCH GmbH