Aryl carbon–chlorine (Ar–Cl) and aryl carbon–fluorine (Ar–F) bond cleavages by rhodium porphyrins

Abstract

Aryl carbon–chlorine (Ar–Cl) bond cleavage has been achieved with rhodium(III) tetrakis-4-tolylporphyrin chloride (Rh(ttp)Cl) to give Rh(ttp)Ar. For 4-chlorofluorobenzene, the aryl carbon–fluorine (Ar–F) bond cleavage competes with the Ar–Cl bond cleavage. Mechanistic investigations show that the Ar–Cl bond cleavage goes through metalloradical ipso-substitution mechanism, while the Ar–F bond cleavage goes through nucleophilic aromatic substitution. The selectivity of the Ar–F or Ar–Cl bond cleavage can be controlled by tuning the temperature and substrate concentration.