From polysubstituted 1,5-dihydro-s-indacene lithium derivatives to polysubstituted hydro-s-indacenyl radicals by a new method involving a single electron transfer from an electron rich olefin

Polyalkyl-hydro-s-indacenyl radicals were obtained from the corresponding polyalkyl-hydro-s-indacenylmonolithium derivatives using a monoelectronic transfer from an electron rich olefin: 1,1′,3,3′-tetramethyl-2,2′-bisimidazolidine (ERO). The reaction involves the transient formation of a polyalkyl-hydro-s-indacenylimidazolidinium salt. The same salt was obtained by another way, reacting imidazolidinium chloride with polyalkyl-hydro-s-indacenyl lithium, and also generates the corresponding polyalkyl-hydro-s-indacenyl radical. All polyalkyl-hydro-s-indacenyl radicals studied present an unsymmetrical spin distribution and, in ESR, hyperfine couplings smaller than those usually observed in similar aromatic radical anions. They were identified from their dimerization products and also by trapping on 2,4,6-tri-tert-butylnitrosobenzene. A rhodium complex radical analog was also studied.

Graphical abstractFrom substituted 1,5-dihydro-s-indacene lithium derivatives, a monoelectronic process (a) provides a new easy route to organic radicals characterized by EPR and spin trapping. The reactional process was established using cross reaction (b).Figure optionsDownload full-size imageDownload as PowerPoint slide