Disclosed a method for preparing a compound of Formula 1, wherein R1 is cyclopropyl, 4-chlorophenyl or 4-bromophenyl; and R2 is C1-C14 alkyl; comprising contacting a compound of Formula 2 with a persulfate oxidant in the presence of a strong sulfur- or phosphorus-containing mineral acid and an oxidation resistant solvent. Also disclosed are methods for preparing the compound of Formula 2 from a compound of Formula 5 as well as compounds of Formula 6 and salts thereof, wherein R is NH2, Cl or OH; X is H or Cl; R1 is cyclopropyl, 4-chlorophenyl or 4-bromophenyl; and R2 is C1-C14 alkyl; provided that when R is NH2 or Cl, then X is Cl; which are useful a process intermediates.