Hydroxylamine → N'-Hydroxy-2-(2-thienyl)ethanimidamide

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290 g. (2.35 moles) of 2-thienylacetonitrile is treated with the equivalent amount of alcoholic hydroxylamine solution and stirred overnight to obtain 2-thienylacetamidoxime. By concentrating, treating the residue with anhydrous chloroform, filtering and again concentrating, the crude amidoxime is obtained in the form of a syrup. The syrupy residue is dissolved in 1000 ml. of anhydrous dioxane and the cooled solution is treated dropwise first with 854 g. of trichloroacetyl chloride then with 380 ml. of pyridine. The mixture is then stirred overnight at room temperature. The dioxane is distilled off in a rotary evaporator and the residue is added to a liter of water. The oily substance which separates is treated with ether. The ether solution is repeatedly washed with water, neutralized with saturated sodium bicarbonate solution, washed several times with water and dried with magnesium sulfate. After concentrating, the residue is treated with 750 ml. of toluene and refluxed in a reflux condensor for about 2 hours. A small amount of water is removed. The toluene solution is treated with activated carbon, filtered, concentrated and the residue is distilled under vacuum. 258 g. of 3-(2-thienylmethyl)-5-(trichloromethyl)-1,2,4-oxadiazole are obtained, b.p. 0.01 119°-122°.

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