Synthesis of aminyl biradicals by base-induced Csp3–Csp3 coupling of cationic azo dyes

摘要

The synthesis of the industrially important polymer parylene is achieved by polymerization of p -quinodimethane ( p -QDM). The polymerization is thought to proceed via a biradical p -QDM dimer, but isolation or characterization of such a biradical has remained elusive. Here, we describe the synthesis of an aza-analogue of this p -QDM dimer. The biradical is formed by base-induced dimerization of an azoimidazolium dye. Due to the presence of sterically shielded aminyl radicals instead of terminal H _(2) ? groups, the stability of this dimer is sufficient for analyses by ESR spectroscopy and X-ray crystallography. A similar Csp ~(3) –Csp ~(3) coupling was observed for an azotriazolium dye, suggesting that base-induced C–C coupling reactions can be realized for different types of azo dyes.