Towards a Scalable Synthesis of 2‐Oxabicyclo[2.2.0]hex‐5‐en‐3‐one Using Flow Photochemistry

• Jason D. Williams^a,b
• Yuma Otake^a
• Guilhem Coussanes^c
• Iakovos Saridakisc^c
• Nuno Maulidec^c
• C. Oliver Kappea^a,b

• ^a Center for Continuous Flow Synthesis and Processing (CC FLOW), Research Center Pharmaceutical Engineering GmbH (RCPE), Inffeldgasse 13, 8010 Graz, Austria
• ^b Institute of Chemistry, University of Graz, NAWI Graz, Heinrichstrasse 28, 8010 Graz, Austria
• ^c Institute of Organic Chemistry, University of Vienna, Währinger Strasse 38, 1090 Vienna, Austria

Cyclobutene lactones hold great potential as synthetic building blocks, yet their preparation by photochemical rearrangement in batch can often be a bottleneck in synthetic studies. We report the use of flow photochemistry as a tool to enable a higher‐throughput approach to the synthesis of 2‐oxabicyclo[2.2.0]hex‐5‐en‐3‐one, which reduces reaction times from 24 hours to 10 minutes. Accordingly, a significantly improved throughput of 144 mg/h (vs 14‐21 mg/h in batch) was achieved. Scale‐out experiments showed problematic reactor fouling, whereby steps were taken to explore and minimize this effect.

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