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Reference : UMR5069-NOENEB-001
Workplace : TOULOUSE
Date of publication : Thursday, April 08, 2021
Scientific Responsible name : Noel NEBRA
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 October 2021
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Description of the thesis topic
Organofluorine compounds exhibit relevant biological properties and have important applications in many fields (pharmacy, agrochemicals and material science, among others). However, the introduction of fluorinated groups in organic backbones (especially in aromatic rings) is not an easy task and no (industrially) efficient methods are known for installing trifluoromethyl groups in a specific position. Over the last few years, many procedures to achieve the aryl-CF3 bond formation via cross-coupling reactions have been developed (typically promoted by palladium and copper complexes), but these methods are not suitable for industrial applications due to their low efficiency and high cost. We seek to develop new alternatives of catalytic trifluoromethylation reactions. Our project targets the preparation of high-valent Ni(IV)CF3 species to achieve the reductive elimination of aryl-CF3 coupled products under mild conditions. Encouraged by the preliminary results carried out in our team (Angew. Chem. Int. Ed. 2017, 56, 12898-12902), we plan to develop an easy access to different high-valent NiCF3 platforms, which will be reacted with a broad variety of organic substrates to afford the trifluoromethylation of many different scaffolds. Combining experimental/theoretical work, this PhD project focuses two long-term goals, namely:
i) the deep understanding about the nature of Ni-CF3 bonds; and
ii) the development of stoichiometric and catalytic processes for aromatic trifluoromethylations induced by Ni-complexes.
Thus, our main goal addresses the isolation and full characterization of aryl-Ni(IV)-CF3 species, and the study of their propensity to promote the reductive elimination of aryl-CF3 coupled products under mild conditions. The acquired information will be decisive in order to achieve the challenging task of developing the unprecedented Ni-catalyzed trifluoromethylation of aromatics via Ni(II)/Ni(IV) redox scenario, and hopefully taking place in a SELECTIVE fashion.
Within the frame of the offered PhD position, two different approaches will be addressed:
i) the use of solvent stabilized high-valent NiCF3 fragments (in both oxidation states +3 and +4); and
ii) the formation of Ni(IV)CF3 complexes [or alternatively, the highly attractive Ni(IV)F species] stabilized by N-donor ligands and the study of their implications in aryl-CF3 (or aryl-F) bond forming reactions.
The PhD associate will work within the SHEN Team, one of the six groups working in the Laboratoire Hétérochimie Fondamentale et Appliquée (LHFA), which is located at Université Paul Sabatier (Toulouse). The SHEN Team is constituted by three permanent researchers/teaching stuff members, and the PhD associate will work upon direct supervision of Dr. Noel Nebra.
The candidate should have a good background in organometallic chemistry and NMR characterization. He/She should be enthusiastic about handling highly sensitive compounds, using a broad range of characterization techniques, discussing results obtained by theoretical calculation, and working as part of a team. Expertise in fluorine chemistry, characterization of transient species, and cross-coupling reactions, will be strongly appreciated.
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