Involved in chloramphenicol biosynthesis (PubMed:24347692, PubMed:25564306). Catalyzes the six-electron oxidation of an aryl-amine precursor of chloramphenicol (NH2-CAM) to yield the aryl-nitro group of chloramphenicol (CAM) (PubMed:24347692, PubMed:25564306, PubMed:27203126). During catalysis, upon exposure of the diferrous cluster to O(2), ClmI forms an exceptionally long-lived peroxo intermediate (CmlI-peroxo), which reacts with NH2-CAM to form CAM (PubMed:25564306, PubMed:27203126). AH2 + alpha-N-dichloroacetyl-p-aminophenylserinol + 2 O2 = A + chloramphenicol + 2 H2O Contains a nonheme dinuclear iron cluster that stabilizes a peroxo intermediate. Antibiotic biosynthesis. Belongs to the AurF N-oxygenase family.