To a 250-ml round-bottomed, three-necked flask equipped with mechanical stirrer, dropping funnel, and condenser with a top outlet tube extending into a saturated barium hydroxide solution is added 7.3 gm (0.10 mole) of propionamide. The flask is placed in a water bath at 40-45°C while 10.9 gm (0.10 mole) of ethyl chloroformate is added rapidly from the dropping funnel. The reaction mixture is rapidly stirred and in 15 min the reaction commences with the evolution of C02 as evidenced by precipitation in the Ba(OH)2 solution. After the carbon dioxide ceases to be evolved the product is washed with anhydrous ether and dried in a vacuum desiccator over cone, sulfuric acid to afford 8.9 gm (65%), m.p. 92-93°C.
The reaction of ethyl chloroformate with N-methyl or N-ethyl alkyla-mides afforded the corresponding N-alkyl imidate hydrochloride, a class of compounds for which no other direct method of synthesis exists. The reaction fails with acetanilide, n-butylacetamide, N-methyl-acetamide, and N-methylcaprylamide. However, thiobenzamide and thio-acetanilide each react with ethyl chloroformate to give ethyl benzimidate hydrochloride and ethyl N-phenylacetaimidate hydrochloride, respectively.
