Several step impurities were identified for R1, R2, and R3 (Figures ). Six impurities were noted in R1, with only three-step impurities each being predicted for R2 and R3. In R1, fluorination of the impurities due to the reaction of the produced impurities with HF, probably as a result of over-reaction, was identified as a key process for the generation of multiple impurities. Interestingly, 1-(4isobutylphenyl) ethanol, which is the intended major product of the following step, R2, was noted as one of the impurities of R1. Also, only one dimerized impurity was observed in the first reaction step.