This invention concerns certain 5-(substituted amino) isothiazoles, compounds of Formula I, and salts thereof, where Q is CN, NHCONRaRb, or CONRaRb, where Ra and Rb are defined herein; and R1 is cyclohexyl, adamantan-1-yl, indan-1-yl, phenyl, benzyl, pyridyl, pyridylmethyl, or pyrimidyl, where all aromatic R1 groups are optionally substituted, provided that when R1 is phenyl, then R1 bears at least one non-alkyl substituent, and further provided that R1 is not 4-chloro-3-trichloromethyl-phenyl; The invention also concerns the tautomeric 5-(substituted amino)-isothiazol-3(2H)-ones, and the use of such compounds to treat Hepatitis C infection. It also concerns thiocarbamoyl acetamides, which are synthetic precursors to the isothiazoles.