RUTHENIUM-CATALYSED REARRANGEMENTS OF AZOBENZENES I. THE PREPARATION OF 1-PHENYLBENZIMIDAZOLES FROM AZOBENZENE DERIVATIVES AND TERTIARY AMINES CATALYSED BY RUTHENIUM COMPLEXES

Article abstract of DOI:10.1016/0022-328X(85)87451-9

Carbonyl complexes of ruthenium catalyse the formation of 1-phenyl-2-alkylbenzimidazole derivatives from azobenzenes and tertiary amines.The reaction involves rearrangement of the azobenzene moiety to an N-phenyl-1,2-phenylenediamine intermediate which then undergoes alkylation at nitrogen with an alkyl group from the tertiary amine followed by ring closure and aromatization.Various ruthenium complexes serve as catalyst precursors for the reaction and the presence of carbon monoxide is required if good yields are to be obtained.RuCl3 * 3H2O is the preferred catalyst precursor.The yields of products formed show a marked dependence on the substituents in the azobenzene derivative.RhCl3 * 3H2O also catalyses the reaction, though less efficiently than ruthenium complexes.