A Convenient Synthetic Route to 2,2'-Biimidazole

Article abstract of DOI:10.1055/s-1986-31607

Convenient two step procedures for the synthesis of 2,2'-biimidazole (3) and its dihydrochloride salt (4) starting with bis-methylimidate (1) in an overall yield of 72 and 83percent, respectively, are reported.Bis-methylimidate (1) was treated with two equivalents of aminoacetaldehyde dimethyl acetal under acid-catalyzed conditions to provide bis-N-(2,2-dimethoxyethylacetamidine) dihydrochloride (2) in 84percent yield.Fusion of 2 with an equivalent of p-toluenesulfonic acid at 200 deg C gave 3 in 86percent yield.Alternatively, 2 was refluxed with 5 molar hydrochloric acid to provide4 as well as 3 in combined yield of 99percent.Evidence is presented for the intermediacy of 2-<4(5)-methoxy-2-imidazolyl>imidazole (5) in the formation of the title compound.Water-soluble 4 is converted to 3 by treatment with potassium carbonate.