Alcl3-Catalyzed C-H P Hosphination Of Benzene: A Mechanistic Study

The characteristics of the reaction for the preparation of dichlomphenylphosphine (DCPP) via benzene and PCl3 in the presence of AlCl3 were studied. Some unique characteristics were observed when a catalytic amount of AlCl3 was used. Namely, more than one mole of DCPP was obtained per mole AlCl3, the reaction solution was layered, and DCPP could be directly separated. Our mechanistic study showed that benzene reacted with PCl3 to form DCPP-AlCl3, and DCPP-AlCl3 dissociated into DCPP and AlCl3, continuing to catalyze this reaction. This resulted in the high catalytic efficiency of AlCl3. The layering of the reaction solution was caused by the immiscibility of DCPP-AlCl3 with the raw materials, greatly facilitating the dissociation process of DCPP-AlCl3. The formation of diphenylphosphorus chloride (DPC) was due to a continuous Friedel-Crafts reaction between DCPP and benzene. DPC cooperated with AlCl3 to form the stable coordination compound DPC-AlCl3 that did not dissociate and was responsible for the deactivation of AlCl3.