Ruthenium Complex Catalyzed N-Heterocyclization. Syntheses of Quinolines and Indole Derivatives from Aminoarenes and 1,3-Propanediol of Glycols

Article abstract of DOI:10.1021/jo00385a006

Aniline reacts with 1,3-propanediol under reflux in diglyme with spontaneous hydrogen evolution in the presence of a catalytic amount of ruth enium trichloride hydrate ( RuCl3*nH2O)-tributylphosphine (PBu3) to give quinoline in good yield.The yield of quinoline was markedly affected by the molar ratios of aniline to 1,3-propanediol and PBu3 to RuCl3*nH2O.The best yield (76percent) was achieved at the molar ratios of 2.5 of aniline / 1,3-propanediol and 2.0 of PBu3 / RuCl3*nH2O.Also, N-substituted anilines react with ethylene glycol in the presence of a catalytic amount of dichlor otris(triphenylphosphine)ruthenium (RuCl2(PPh3)3) to give N-substituted indole derivatives.The reactions were carried out at 180 deg C in dioxane with spontaneus hydrogen evolution.Aminoarenes also react with 2,3-butanediol and 1,2-cyclohexanediol ( mixture of cis and trans ) in the presence of RuCl2(PPh3)3 to give the corresponding 2,3-dimethylindoles and 1,2,3,4-tetrahydrocarbazoles in good to excellent yields.As the key intermediates of the reactions, N,N'-diarylpropylenediamine (5a) and N,N'-diarylethylenediamine (5b) and their dehydrogenated imine derivatives are postulated.