First intramolecular aromatic substitution by gold(III) of a ligand other than pyridine derivatives. Synthesis and crystal structure of the novel five-membered cycloaurated complex of 1-ethyl-2-phenylimidazole

Reactions of gold(III) compounds, AuCl3·4H2O and HAuCl4·4H2O, with 2-phenyl-1H-imidazole (Hpi) and 1-ethyl-2-phenylimidazole (Hepi) have been performed under various reaction conditions: Hpi afforded only the salt [H(Hpi)][AuCl4], while Hepi produced both the salt [H(Hepi)][AuCl4] and the adduct [AuCl3(Hepi)]. Cycloauration of Hepi, the first example of cycloauration of a substrate other than pyridine derivatives, has been established by the formation of [AuCl2(epi-C1,N)] [epi = 2-(1-ethyl-2-imidazolyl)phenyl] from the reaction between the adduct [AuCl3(Hepi)] and AgBF4. The cyclometallated structure of Hepi has been confirmed by the X-ray crystallographic study of a derivative [AuCl(epi-C1,N)(PPh3)]PF6.