Divergent Role of PIDA and PIFA in the AlX₃ (X=Cl, Br) Halogenation of 2 Naphthol: A Mechanistic Study

The chlorination and bromination reaction mechanisms of 2-naphthol under the previously reported PIDA- or PIFA-AlX 3 (X= Cl, Br) systems by our research group, was elucidated via quantum chemical calculations within the density functional theory. The studied chlorination mechanism using PIFA and AlCl 3 demonstrated better experimental and theoretical yields than when PIDA was used. Additionally, the lowest-in-energy chlorinating species involve an equilibrium between the Cl-I(Ph)-OTFA-AlCl 3 and [Cl-I(Ph)+] [-OTFA-AlCl 3 ] species more than the PhICl 2 formation. On the other hand, the bromination mechanism was more efficient using PIDA and AlBr 3 to form the intermediate Br-I(Ph)-OAc-AlBr 3 as the brominating active species. Similarly, the PhIBr 2 is higher-in-energy than our proposal. The detailed reaction mechanisms described in this work are in excellent agreement with the experimental yields. These initial results confirm that such mechanisms are energetically more likely to occur, forming the equilibrium species than in the presence of the corresponding halogenating PhIX 2 .