Rapid CO2 coupling to propargylic alcohols: unlocking the production of α-alkylidene cyclic carbonates via continuous flow

alpha-Alkylidene cyclic carbonates (alpha CCs) are gaining interest as building blocks in organic and polymer chemistry. To date, their synthesis via the coupling of CO2 to propargylic alcohols has been restricted to batch processes, with extensive efforts devoted to improving catalytic systems. Herein, utilizing a refined, homogeneous silver-carbene-organobase catalytic system, we optimized batch conditions to achieve, for the first time, complete conversion of tertiary propargylic alcohols within minutes instead of hours. Building on this, we introduce a continuous flow methodology to produce a library of alpha CCs, achieving the highest space-time yields reported, with quantitative conversions in less than 20 minutes and outputs up to 111 grams per day. This approach reduces CO2 usage to 1 or 2 equivalents, improves parameter control, and is expected to facilitate scalability. In addition, "plug-and-play" lab-scale continuous flow modules enable seamless integration of subsequent alpha CC transformations without intermediate purification, as illustrated by the aminolysis of alpha CCs into oxazolidones with good conversion (91%). Furthermore, supporting the silver-carbene catalyst on a polymer matrix eliminates silver contamination and even suppresses the need for a base co-catalyst. This work advances the scalable synthesis of alpha CCs via continuous flow, marking a significant step toward greener, CO2-based cyclic carbonates and derivatives.