The impact of Novel Process Windows on the Claisen rearrangement

作者：Kobayashi Hiroki; Driessen Brian; van Osch Dannie J G P; Talla Ali; Ookawara Shinichi; Noel Timothy^*; Hessel Volker

来源：Tetrahedron, 2013, 69(14): 2885-2890.

DOI：10.1016/j.tet.2013.02.038

• Microreactors
• Novel Process Windows
• Flow chemistry
• Claisen
• High temperature

The impact of Novel Process Windows on the Claisen rearrangement in microflow was investigated. Elevated temperatures (up to 300 degrees C) were crucial to achieve full conversion of allyl phenyl ether in the Claisen rearrangement. We observed that 1-butanol was the optimal reaction solvent for this transformation in flow. Solvent-free reaction conditions were feasible for the Claisen rearrangement and provided quantitative yields of the target product at 280 degrees C and 100 bar. Also elevated reaction pressures (up to 300 bar) were investigated in the Claisen rearrangement. We found that thermal expansion and pressure-related compression phenomena cannot be ignored at such harsh reaction conditions. These phenomena lead to large deviations of the desired residence time (as calculated from the nominal flow rate) and have a clear impact on the observed reaction trends. Finally, we also investigated the temperature effect on the Johnson-Claisen rearrangement of cinnamyl alcohol. Quantitative yields were obtained at 200 degrees C and at 100 bar.

• 出版日期2013-4-8