Fusion of Four Aromatic Rings via an Atom-Mutual-Embedding Strategy to Form a Tetrahexacyclic System

Abstract

Skeletal manipulation of aromatic compounds has emerged as a potent tool in synthetic chemistry, but simultaneous multiring manipulation remains largely unexplored due to the inherent complexities of ring and site selectivity. Herein, we report an unprecedented multiring skeletal manipulation that fuses four 5-membered aromatic rings, comprising two organic and two metal-containing aromatic systems, into a novel metal-bridged 6/6/6/6-membered ring scaffold. The sequential ring fusion is accomplished through an atom-mutual-embedding strategy; this strategy entails the stepwise insertion of two nitrogen atoms into separate metal–carbon bonds and simultaneously integrates a metal atom as a bridge across two isoxazole moieties. The presence of a central metal atom is crucial for ensuring precise substrate alignment and enhancing both the ring and site specificity. The resulting tetrahexacyclic products exhibit remarkable stability and superior near-infrared (NIR) functional properties, surpassing those of the precursor compounds. This work not only establishes a conceptual foundation for designing versatile substrate molecules amenable to intricate editing but also contributes to the rational and performance-targeted manipulation of molecular architectures.