Synthesis of spiro[4.4]nonane-containing functional organic molecules

<h2>Abstract</h2> Spiro[4.4]nonane features are an important scaffold in many applications such as enantioenriched ligands, functional materials, natural products, and polymers. Excited by the prospect of the spiro[4.4]nonane scaffold, its structural intricacy still appears challenging in chemical synthesis. Many functional organic molecules possessing spiro[4.4]nonane scaffold(s) have recently been reported and synthesized. We provide a <i>Minireview</i> highlighting such advancements and discuss the future opportunities of spiro[4.4]nonane scaffolds in organic chemistry. Representative examples from 2019 to 2024 are discussed.