Formal [2+1] Cycloadditions of a Metallacyclopentadiene Unit with Alkynes: Constructing Tetracyclic Conjugated Frameworks with Bridgehead Metals

Abstract

Comprehensive Summary Metallacyclopentadienes play a vital role in transition‐metal mediated and catalyzed cycloaddition reactions of alkynes. Though versatile reactions of metallacyclopentadienes with alkynes have been disclosed, [2+1] cycloadditions of metallacyclopentadienes and alkynes have never been discovered. In present work, we report the formal [2+1] cycloadditions of a metallacyclopentadiene unit with a broad scope of commercial alkynes, providing a facile strategy to construct tetracyclic conjugated compounds. The deuterated experiment indicates a metal vinylidene intermediate has been involved in [2+1] cycloaddition. Moreover, the electrophilic substitution reaction of the tetracyclic conjugated compound with the aid of density functional theory (DFT) calculated Fukui functions is investigated. These tetracyclic conjugated compounds exhibit broad absorption spectra in the whole visible region which could be employed as potential photovoltaic materials.

Preparation and Aromaticity of Rhenacycloprop-2-ene-containing Polycyclic Compounds

“…Aromaticity study of metallacycloprop-1-ene complexes has been reported recently, − and they show mainly σ-aromaticity. Such work on metallacycloprop-2-ene complexes is less developed though η 2 -alkyne complexes have been widely studied. ,− Since many fused metallacycloprop-1-enes are aromatic, − herein we present the synthesis and characterization of fused five- and six-membered oxa-rhenacycles with a metallacycloprop-2-ene unit, as well as their aromaticity investigation.…”