Thiocyanation of indoles

Treatment of indole, 2-phenylindole, 2-methylindole, and ethyl indole-2-carboxylate with thiocyanogen in acetic acid at 0° afforded the corresponding 3-thiocyanatoindoles in quantitative yields, whereas similar treatment of 3-methyl-2-phenylindoles and 2,3-diphenylindoles gave the corresponding 6-thiocyanatoindoles in high yields.