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<p>The formation of chiral organic molecules from Friedel–Crafts reactions of chiral alcohols has been deemed impractical due to racemization via carbocation formation. Here we demonstrate the preservation of stereochemistry in intramolecular Friedel–Crafts alkylation reactions, expanding the boundaries of accessible chiral chemistry. Mechanistic investigations show that the retention of stereochemistry stems from the chirality memory of transient, axially chiral carbocation intermediates. This finding allows the synthesis of axially chiral spirocarbon-bridged conjugated carbocycles. Leveraging a rhodium-catalysed regioselective C–H activation–annulation approach, the reaction of thiobenzamide with phenylethynyl tertiary alcohol is a crucial step in expanding the spiro-bridged skeleton. We used this approach to develop an iterative synthetic sequence to construct enantiopure spirocarbon-bridged pure-hydrocarbon oligo(<i>trans</i>-stilbene) compounds. Notably, in the concluding step of the iterative synthesis, all chiral tertiary alcohol units undergo a stereospecific one-shot conversion to form multiple spirocyclic structures, resembling a ‘zipping up’ process. This synthetic strategy facilitates both the longitudinal and lateral extension of spiro-bridged conjugated structures, with promising applications in circularly polarized lasers.</p><p></p>

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Chirality retention in Friedel–Crafts spiroannulation for iterative synthesis of spiro-bridged conjugated carbocycles

  • 期刊论文

  • 发表日期：

    2025年6月2日

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  • Xingwen Pu,
  • Yi Lu,
  • Zhonghao Zhou,
  • Yudong Yang,
  • Cheng Zhang,
  • Peiyuan Yu,
  • Yong Sheng Zhao,
  • Jingbo Lan,
  • Jingsong You

摘要

The formation of chiral organic molecules from Friedel–Crafts reactions of chiral alcohols has been deemed impractical due to racemization via carbocation formation. Here we demonstrate the preservation of stereochemistry in intramolecular Friedel–Crafts alkylation reactions, expanding the boundaries of accessible chiral chemistry. Mechanistic investigations show that the retention of stereochemistry stems from the chirality memory of transient, axially chiral carbocation intermediates. This finding allows the synthesis of axially chiral spirocarbon-bridged conjugated carbocycles. Leveraging a rhodium-catalysed regioselective C–H activation–annulation approach, the reaction of thiobenzamide with phenylethynyl tertiary alcohol is a crucial step in expanding the spiro-bridged skeleton. We used this approach to develop an iterative synthetic sequence to construct enantiopure spirocarbon-bridged pure-hydrocarbon oligo(trans-stilbene) compounds. Notably, in the concluding step of the iterative synthesis, all chiral tertiary alcohol units undergo a stereospecific one-shot conversion to form multiple spirocyclic structures, resembling a ‘zipping up’ process. This synthetic strategy facilitates both the longitudinal and lateral extension of spiro-bridged conjugated structures, with promising applications in circularly polarized lasers.