BAMBERGER FISSION AND RECLOSURE OF 1-ALKYL-5-(ALKYLAMINO)IMIDAZOLE-4-CARBONITRILES LEADING TO THEIR 2-OXO DERIVATIVES

1-Methyl-5-(methylamino)imidazole-4-carbonitrile (4a) afforded three m inor ring-opened products (5a, 6a, 10a) besides its 2-oxo derivative 3 a on treatment with ethyl chloroformate in aqueous sodium bicarbonate. The geometrical isomers of these trisubstituted propenenitriles (5a, 6a, 10a) can be separated from each other by means of TLC, but equilib rate rapidly in solution. Because these compounds were converted into 3a in aqueous sodium hydroxide, alkaline treatment of the reaction mix ture of 4a afforded a higher yield of 3a; although 3a also rapidly cha nged into other compounds in 0.1N aqueous sodium hydroxide at room tem perature, it could be recovered from the solution in high yield. 5-Alk ylamino homologues 3b,c were also prepared in 64% and 46% yields, resp ectively, by similar treatment of the substrates 4b,c having the 5-alk ylamino substituents. The same products 3b,c were obtainable from the positional isomers 4d,e in 83% and 51% yields, respectively. These out comes are interpretable by supposing that the reactions proceed throug h common intermediates, equilibrated mixtures of (E)- and lkylamino)-1 -cyano-2-(methylamino)ethenyl]carbamic acid ethyl eaters (7).