secondary alkylamines with activemethylenecompounds afforded mono-sulfenylated compounds in good yields. The reactions of 2 mol of sulfenamides derived from imides with 1 mol of activemethylenecompounds in the presence of a base gave di-sulfenylated compounds. It was found that α-mono-sulfenylated ketones were prepared by the reactions of enamines with sulfenamides derived from imides. α-gem-Di-sulfenylated
N-alkenyltetracycline derivatives, for example, N-(1-methyl-2-.alpha.-naphthylethenyl)tetracycline represented by the formula ##SPC1## The compounds have excellent antibacterial action as compared with tetracycline.