In-line Multidimensional NMR Monitoring of Photochemical Flow Reactions

This work demonstrates the in-line monitoring of a flow photochemical reaction using 1D and ultrafast 2D NMR methods at high magnetic field. The reaction mixture exiting the flow reactor is flown through the NMR spectrometer and directly analyzed. In the case of simple substrates, suitable information can be obtained through 1D H-1 spectra, but for molecules of higher complexity the use of 2D experiments is key to address signal overlaps and assignment issues. Here we show the usefulness of ultrafast 2D COSY experiments acquired in 70 s or less, for the in-line monitoring of photochemical reactions, and the possibility to obtain reliable quantitative information. This is a powerful framework to, for example, efficiently screen reaction conditions.

Automated summary

This work demonstrates the online monitoring of a flow photochemical reaction using advanced NMR methods. By analyzing the reaction mixture directly, both 1D and ultrafast 2D experiments provide valuable information, especially for complex molecules. The study highlights the efficiency of ultrafast 2D COSY experiments for real-time monitoring and quantitative analysis, enabling effective screening of reaction conditions.