The Microwave-to-Flow Paradigm: Translating High-Temperature Batch Microwave Chemistry to Scalable Continuous-Flow Processes

• Published in: Chemistry : a European journal Vol. 17; no. 43; pp. 11956 - 11968
• Main Authors: Glasnov, Toma N., Kappe, C. Oliver
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 17-10-2011; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: Chemistry; flow chemistry; high-temperature chemistry; microreactors; microwave chemistry; process intensification; synthetic methods; Temperature
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201102065

The popularity of dedicated microwave reactors in many academic and industrial laboratories has produced a plethora of synthetic protocols that are based on this enabling technology. In the majority of examples, transformations that require several hours when performed using conventional heating under reflux conditions reach completion in a few minutes or even seconds in sealed‐vessel, autoclave‐type, microwave reactors. However, one severe drawback of microwave chemistry is the difficulty in scaling this technology to a production‐scale level. This Concept article demonstrates that this limitation can be overcome by translating batch microwave chemistry to scalable continuous‐flow processes. For this purpose, conventionally heated micro‐ or mesofluidic flow devices fitted with a back‐pressure regulator are employed, in which the high temperatures and pressures attainable in a sealed‐vessel microwave chemistry batch experiment can be mimicked.
Microwaves not required! Conventionally heated flow reactors (coils or chips) fitted with back‐pressure regulators can mimic the high temperatures and pressures attainable in a sealed‐vessel microwave instrument. Such devices can therefore be used to perform otherwise difficult to scale microwave chemistry (see scheme).