We have synthesized 2-(thienyl-2)imidazole and its N-methyl derivative. The latter product was obtained by nitration, bromination, acylation, and formylation, occurring as a rule on the thiophene ring. A general method for methylating 2-R-imidazoles with methyl iodide KOH--dimethoxy ethane is proposed.
We have previously studied electrophilic substitution reactions of 1-methyl-2-(furyi-2)imidazole (I) [1]. Here we report the synthesis and investigation of the hitherto undescribed 1-methyl-2(thienyl-2)imidazole (II). f CH~ I, II I X=O; II X=~
Reaction of aqueous ethylenediamine with thiophene-2-carboxylic acid as in [2] gave in 84% yield 2-(thienyl-2)imidazoline (III). On reflux in diphenyl oxide in the presence of 2% palladium on carbon, the product rapidly dehydrogenated to give 2-(thienyl-2)imidazole (IV). However, the reaction did not go to conclusion, probably due to poisoning of the catalyst with sulfur-containing degradation products of the thiophene ring. The mixture of III and IV could not be separated by fractional crystallization or column chromatography. Their different reactions with silver nitrate afforded a separation. Imidazole IV formed an insoluble salt, while imidazoline III gave a complex soluble in DMF and partly soluble in other solvents. *For Communication 1 see [1].