Continuous-flow synthesis of fluorine-containing fine chemicals with integrated benchtop NMR analysis

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Abstract

Fluorine fine chemical synthesis takes a step ahead using integrated NMR online-analysis with a benchtop NMR spectrometer.

Abstract

A compact lab plant was designed for the continuous-flow synthesis of fluorine-containing compounds and was combined with an NMR analysis platform based on a benchtop NMR spectrometer. The approach of a unified synthesis and analysis strategy for fine chemicals was applied to three different reactions, all employing fluorine as a chemical probe for online- ¹⁹F NMR analysis. A high temperature synthesis for the deprotection of a CF ₂H group was done as well as Ruppert–Prakash reactions for the perfluoroalkylation of benzaldehyde as a model substrate. The C–H arylation of furan with a trifluoromethylated aryldiazonium salt was performed as an example of a photochemically catalyzed reaction. All three reaction classes challenge the synthesis and analysis setup differently according to sample preparation (premagnetization of bubble-free sample) and spectrometer sensitivity (signal to noise ratio, spectral resolution, scan number, substrate concentration and flow rate), but nonetheless prove the successful application of the continuous-flow synthesis of fluorinated fine chemicals with integrated online NMR analysis.

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The Unique Role of Fluorine in the Design of Active Ingredients for Modern Crop Protection

Peter Jeschke (2004)

The task of inventing and developing active ingredients with useful biological activities requires a search for novel chemical substructures. This process may trigger the discovery of whole classes of chemicals of potential commercial interest. Similar biological effects can often be achieved by completely different compounds. However, compounds within a given structural family may exhibit quite different biological activities depending on their interactions with different intracellular proteins like enzymes or receptors. By varying the functional groups and structural elements of a lead compound, its interaction with the active site of the target protein, as well as its physicochemical, pharmacokinetic, and dynamic properties can be improved. In this context, the introduction of fluorine into active ingredients has become an important concept in the quest for a modern crop protection product with optimal efficacy, environmental safety, user friendliness, and economic viability. Fluorinated organic compounds represent an important and growing family of commercial agrochemicals. A number of recently developed agrochemical candidates represent novel classes of chemical compounds with new modes of action; several of these compounds contain new fluorinated substituents. However, the complex structure-activity relationships associated with biologically active molecules mean that the introduction of fluorine can lead to either an increase or a decrease in the efficacy of a compound depending on its changed mode of action, physicochemical properties, target interaction, or metabolic susceptibility and transformation. Therefore, it is still difficult to predict the sites in a molecule at which fluorine substitution will result in optimal desired effects.

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Metal-free, visible-light-mediated direct C-H arylation of heteroarenes with aryl diazonium salts.

Durga Prasad Hari, Peter Schroll, Burkhard König … (2012)

Visible light along with 1 mol % eosin Y catalyzes the direct C-H bond arylation of heteroarenes with aryl diazonium salts by a photoredox process. We have investigated the scope of the reaction for several aryl diazonium salts and heteroarenes. The general and easy procedure provides a transition-metal-free alternative for the formation of aryl-heteroaryl bonds.