Taking inspiration from previous self-optimized flow systems employing in-line analytical monitoring, researchers from the University of Glasgow (UK) have developed a method allowing performance of multinuclear and 2D NMR in the fume hood.
In addition to performing in-line 1H, 13C, 19F and 2D NMR analysis, the group, led by Lee Cronin (University of Glasgow) combined in-line 1H NMR with computational techniques to develop a self-optimizing reactor. Their benchtop technology utilizes simple plastic tubing and non-deuterated solvents to integrate NMR monitoring into a flow system.
In tests, the reactor followed an acid-catalyzed reaction between a benzaldehyde and aniline through the integration of specific peaks in the NMR spectra in order to assess the reaction yield. This data was fed back in order to allow automatic adjustment of the reaction parameters and real-time maximization of the yield. This ability is key to the concept of ‘dial-a-molecule’ synthesis, the ability to automate optimization of a reaction via feedback control.
Previous systems aiming to integrate in-line NMR spectroscopy have been limited to bypass configurations, flow cells in high-field magnets or microfluidics. In contrast, this novel approach takes advantage of a compact permanent low-field magnet that can be used even in the presence of other magnetic equipment or materials.
Discussing his group’s work, Cronin stated: ‘We hope that people will be inspired to use spectroscopy to monitor reactions in-flow and use it to dynamically control the reaction process parameters.” The team hope to further their technology by combining multiple spectroscopies with more advanced algorithms.
Sources: Sans V, Porwol L, Dragonea V, Cronin L. A self optimizing synthetic organic reactor system using real-time in-line NMR spectroscopy. Chem. Sci. DOI:10.1039/C4SC03075C (2014) (Epub ahead of print); Benchtop NMR gives feedback in flow.