From screening to the hectogram scale: sustainable electrochemical synthesis of mefenpyr-diethyl

Abstract

To demonstrate the technical application potential of electrochemical reactions, we developed a synthetic method to access commercially available herbicide safener mefenpyr-diethyl. In a simple undivided electrolysis cell with non-hazardous aqueous...

Biphasic Electrosynthesis of 2-Isoxazol(in)e-3-carboxylates: Reaction Optimization from Milligram to Hectogram Scale

“…Mechanistic Considerations. Based on the described findings and in accordance to previous reports, 28,33,39,49 the following mechanism is proposed (Scheme 6): Similar to the mechanism described by Shono et al, 28 iodide is, in a first step, anodically oxidized to triiodide in the aqueous layer. At the phase boundary, oxime 5 is then oxidized by triiodide in analogy to the mechanism for the oxidation of oximes with NCS proposed by Togo and Kobayashi.…”

“…The envisioned setup was based on methods for the electro-organic synthesis of pyrazolines and pyrazoles published by Waldvogel et al ,, Starting from the reported conditions for the pyrazoline synthesis from glyoxylate hydrazones, a transfer on the conversion of ethyl 2-(hydroxyimino)­acetate (Scheme , 5b ) and the reaction of the corresponding nitrile oxide with styrene was attempted. The appropriate supporting electrolyte, electrode material, and solvent were tested first (see Table S4).…”

Overview of Recent Scale-Ups in Organic Electrosynthesis (2000–2023)

“…Waldvogel, in collaboration with Bayer, reported the synthesis of the herbicide mefenpyr-diethyl from 2,4-dichlorophenylhydrazone hydrochloride via electrolysis of either (Z)-hydrazone 39 or (E)-hydrazone 40 and methacrylate to afford 41 (Scheme 16). 121 The oxidation was achieved using a 1.5 L jacketed glass vessel equipped with six graphite electrodes and aqueous sodium iodide, which serves as both the supporting electrolyte and the mediator. The oxidative cyclization was done on 209 g of 39 and 42 g of 40, achieving comparable yields of 66% and 63% yield, respectively.…”

Dual Roles of Supporting Electrolytes in Organic Electrosynthesis

“…The commercial herbicide safener mefenpyr-diethyl synthesis was presented as a highlight for this elegant and scalable protocol, allowing hectogram quantities. [64] A different iodide-mediated protocol was reported for the electrochemical synthesis of aziridines via the NÀ H bond activation (Scheme 18c). [65] With potassium iodide as a mediator role, external oxidants are avoided, and the reaction is complimented by the cathodic evolution of hydrogen as the byproduct.…”