2D BC NMR reaction monitoring
Benchtop NMR spectrometers for the in-line monitoring of continuous flow reactions

Naturally, online ¹⁹F NMR tracking is only possible in a limited number of situations where the product of interest carries a fluorine atom. Thus, in the absence of ¹⁹F nuclei and if ¹H spectra prove too complex to analyze, even after solvent exchange (protonated → deuterated), reaction tracking can be carried out using 2-dimensional sequences. The use of 2-D NMR experiments, where resonances are recorded on a 2-D map, makes sense at low fields thanks to a significant gain in signal separation. As such, numerous homo- and heteronuclear sequences, including ultrafast methodologies, have already been developed on low-field benchtop spectrometers as discussed in section II, although not all of these tools have yet been used for monitoring reactions conducted in continuous flow.

Ley's team has developed a flow reactor using low-field 2D NMR on-line monitoring to...