A Divergent Synthesis of Spiroindenes via Ligand-Controlled [3+2]/[4+2] Cycloadditions of Zwitterionic π-Propargyl Palladium Species with Benzofulvenes

Yongjie Long; Xianhua Zhong; Min Shi; Yin Wei

doi:10.1002/cjoc.202401301

Chinese Journal of Chemistry ›› 2025, Vol. 43 ›› Issue (10) : 1181 -1189. DOI: 10.1002/cjoc.202401301

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A Divergent Synthesis of Spiroindenes via Ligand-Controlled [3+2]/[4+2] Cycloadditions of Zwitterionic π-Propargyl Palladium Species with Benzofulvenes

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Abstract

A divergent synthesis of spiroindenes through a palladium catalyzed cycloaddition between zwitterionic π-propargyl palladium species and benzofulvenes in moderate to good yields has been disclosed along with good functional group compatibility and a broad substrate universality. This protocol features a highly regioselective switchable process between [3+2] and [4+2] cycloadditions controlled by phosphine ligands with different bite angles. The reaction mechanism has been clarified by mechanistic studies and DFT calculations, rendering that the coordination modes of the ligands with the substrates and the bite angle of the ligands play critical roles in the product regioselectivity.

Keywords

Zwitterions / Palladium catalyzed / Divergent synthesis / Ligand control / Spiro compounds / π-Propargyl palladium species / Annulation

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Yongjie Long, Xianhua Zhong, Min Shi, Yin Wei. A Divergent Synthesis of Spiroindenes via Ligand-Controlled [3+2]/[4+2] Cycloadditions of Zwitterionic π-Propargyl Palladium Species with Benzofulvenes. Chinese Journal of Chemistry, 2025, 43(10): 1181-1189 DOI:10.1002/cjoc.202401301