Flowmicro In‐Line Analysis‐Driven Design of Reactions Mediated by Unstable Intermediates: Flash Monitoring Approach

The direct observation of reactive intermediates is an important issue for organic synthesis. However, intermediates with an extreme instability are hard to be monitored by common spectroscopic methods such as FTIR. We have developed synthetic method utilizing flow microreactors, which enables a generation and reactions of unstable intermediates. Herein we report that, based on our flowmicro techniques, we developed an in‐line analysis method for reactive intermediates in increments of milliseconds. We demonstrated the direct observation of the living and dead species of the anionic polymerization of alkyl methacrylates. The direct information of the living species enabled the anionic polymerization and copolymerization of oligo(ethylene glycol) methyl ether methacrylates, which is the important but difficult reaction in the conventional method. Flash monitoring: Direct observation of anionic polymerizing methacrylates was achieved by utilizing flow microreactors, which can transfer the unstable intermediates to spectroscopic instrument before they decompose. The in‐line analysis of poly(methacrylate) anions revealed their structure, stability, and livingness, enabling the anionic polymerization and copolymerization of oligo(ethylene glycol) methyl ether methacrylates.