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Efficient Synthesis of All-Carbon Quaternary Centers via the Conjugate Addition of Functionalized Monoorganozinc Bromides

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Cyclopentannulation Approach to Functionalized Diquinanes and Angularquinanes: Concise Total Synthesis of

Ananth Kumar Ballari¹, Snehasish Senapati¹, Sandesh D P¹

¹Department of Chemistry, Indian Institute of Technology Tirupati, Yerpedu-Venkatagiri Road, Yerpedu Post, Tirupati District, Andhra Pradesh 517619, India.

The Journal of Organic Chemistry

|August 8, 2025

Abstract:

A general and efficient approach for the short synthesis of functionalized diquinanes and angular quinanes is described. This strategy involves cyclopentannulation of 2-alkyl-substituted cyclic 1,3-pentanediones with a cyclopropyl phosphonium salt ([1-(ethoxycarbonyl)cyclopropyl]triphenylphosphonium tetrafluoroborate), enabling the incorporation of diverse substituents at the bridgehead position of diquinanes. The resulting cyclopentannulation products can be readily transformed into synthetically challenging diquinanes containing two vicinal quaternary carbon stereocenters and multiple stereocenters and linear triquinanes. The application of this method is demonstrated by a concise total synthesis of chondrosterins I and J.

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