To further verify the importance of flow conditions, batch reactions were examined under the same reaction conditions except for reaction time (10 s) because it was difficult to perform batch reactions exactly within 2.5 s (Table ). The reaction conditions included in the Pareto front were used, and three independent experiments were carried out. Although the reaction mixture was vigorously stirred (1,000 rpm) under the batch conditions, the yield decreased by ca. 35% compared to flow conditions. It is considered that efficient mixing was achieved in flow, resulting in a higher yield, while mixing in batch conditions was insufficient. In addition, generation of toxic gaseous hydrogen chloride was observed in batch. Therefore, scaled-up of this reaction under batch conditions could be problematic.