Herein, we present the BF3/BF4- mediated activation of diphenyl phosphite for the formation of thionium ions from aldehydes and thiophenols. These reactive species subsequently undergo reaction with in situ generated phenol, resulting in the synthesis of diarylmethyl thioethers. It was demonstrated that the addition of external phenol in the reaction produced unsymmetrical gem-diarylmethyl thioethers in good yields.