SENGMANY Stéphane

The research topic that we are developing focuses on organic electrosynthesis as an alternative tool to perform various molecular transformations. Electrosynthesis constitutes a mild and selective method allowing to meet the challenges of organic synthesis, both in reducing and oxidizing processes, where conventional chemical pathways have not necessarily provided solutions.

Developed in the laboratory in the 90s, the sacrficial anode process allows, under intensiostatic conditions, in the presence of a transition metal salt catalyst (nickel, copper, iron, …), to activate carbon-halogen bonds of organic compounds to achieve chemical transformations without membrane separation and under operating conditions that do not require the use of anhydrous solvents.

Our initial work focused on the synthesis of 3-membered rings from polyhalomethylated substrates and α-activated olefins, or aldehydes/ketones, or imines, in the presence of catalytic amounts of transition metal salts. The sacrificial anode process, combined with transition metal catalysis, allows to avoid the directe reduction of the substrates and to access to the formation of key intermediates.

This nickel-catalyzed electrochemical process was subsequently extended to aromatic and heteroaromatic halides for C(sp²)-C(sp³) bond formation such as conjugate addition reactions with activated olefins (to access to medium-sized benzolactone precursors) and C(sp²)-C(sp²) bond formation with (hetero)aromatic halides for homocouplings and/or cross-couplings.

During this work, we have shown the interest of using an electrochemical step in the preparation of medium-sized benzolactone precursors. The arylation of activated olefins by electrochemical approach, developed by S. Condon in the laboratory, has found its application in the preparation of hydroxy acid precursors leading to these medium size benzolactones (7 to 11-membered lactones). The scheme below shows the 2 synthesis routes that have been achieved.

Various studies allowed to synthesize bi(hetero)aryl compounds by coupling chlorodiazines (pyridazine, pyrimidines and pyrazine) with (hetero)aromatic halides.

The analytical study by cyclic voltammetry allowed to highlight a key reaction intermediate and to propose a nickel-catalyzed reaction mechanism. The synthesized molecules can be used as precursors for access to materials or ligands and, for some of them, present a cytotoxic activity towards cancer cell lines.

α-Aminophosphonates could be prepared in an undivided electrochemical cell combining simultaneously cathodic and anodic processes. This work was featured on the cover of an issue of Synlett (July 2020).

• Bachelor level
  • Organic Chemistry, 2^nd year (tutorials, practical courses)
  • Mechanism and Theories in Organic Chemistry, 2^nd year (tutorials)
  • Multi-Step Organic Synthesis, 3^rd year (tutorials, practical courses)
  • Experimental and Organometallic Chemistry, 3^rd year (tutorials, practical courses)
• Master level
  • Strategies of Synthesis in Fine Chemistry 2, Master 1 (lectures, practical courses)
  • Heterocyclic Chemistry, Master 2 (lectures)