AlCl3-catalyzed C-H p hosphination of benzene: A mechanistic study

The characteristics of the reaction for the preparation of dichlorophenylphosphine (DCPP) via benzene and PCl 3 in the presence of AlCl 3 were studied. Some unique characteristics were observed when a catalytic amount of AlCl 3 was used. Namely, more than one mole of DCPP was obtained per mole AlCl 3 , the reaction solution was layered, and DCPP could be directly separated. Our mechanistic study showed that benzene reacted with PCl 3 to form DCPP-AlCl 3 , and DCPP-AlCl 3 dissociated into DCPP and AlCl 3 , continuing to catalyze this reaction. This resulted in the high catalytic efficiency of AlCl 3 . The layering of the reaction solution was caused by the immiscibility of DCPP-AlCl 3 with the raw materials, greatly facilitating the dissociation process of DCPP-AlCl 3 . The formation of diphenylphosphorus chloride (DPC) was due to a continuous Friedel-Crafts reaction between DCPP and benzene. DPC cooperated with AlCl 3 to form the stable coordination compound DPC-AlCl 3 that did not dissociate and was responsible for the deactivation of AlCl 3 .