Effective Utilization of Flow Chemistry: Use of Unstable Intermediates, Inhibition of Side Reactions, and Scale-Up for Boronic Acid Synthesis

Flow chemistry processes for boronic acid syntheses utilizing lithiation–borylation have been developed. The side reactions in the lithiation step that occur in batch were suppressed, and unstable lithium intermediates were handled safely. Flow technology was applied to several kinds of boronic acid syntheses, and scale-up was successfully conducted to allow kilogram-scale production. Some of the key benefits of flow flash chemistry were utilized, both to avoid side reactions and to enable dianion chemistry that is difficult to perform successfully in batch reactions. The examples showed further perspectives on the utility of flow technologies for process development.