Selective Transformations of Allylic Compounds and Enol Derivatives : Synthesis of Fluorinated and Nitrogenated Scaffolds

Abstract: In this thesis, new synthetic methods to give access to molecules having fluorinated scaffolds and other polar functional groups have been developed. The methods give access to highly valuable organic compounds that may serve as building blocks in the synthesis of functionalized drug candidates. In particular, the present thesis describes four new protocols for the synthesis of such compounds starting from allylic substrates and enol derivatives, using metal- or organocatalysts.In the introductory chapter (Chapter 1), the importance and the different approaches to catalysis are discussed. The structural features and reactivity of allylic substrates are presented, followed by an extensive description of the use of CO2 as a building block in organic synthesis. In the final part of this chapter, the structure and common reactive pathways of hypervalent iodine(III) reagents are described.In the second part (Chapter 2), a palladium-catalyzed allylic substitution method is designed to obtain 3-fluoropiperidines from 1,3-dicarbonyl compounds and allylic carbamates. The final products are further functionalized in a chemo- and diastereoselective manner. Additionally, the enantioselective version of this reaction is studied using chiral phosphoramidite ligands.In the third chapter, an umpolung methodology for CO2 fixation is explored in the coupling of silyl enol ethers with amines and CO2 mediated by hypervalent iodine(III) reagents. The mechanism of this transformation is examined using DFT calculations and experimental results. Moreover, this protocol is extended to 1,3-dicarbonyl compounds, yielding α-carbamate-β-ketocarbonyl compounds.The final part of this thesis (Chapter IV and V) describes the base-catalyzed stereospecific isomerization of allylic halides and amines. Catalytic amounts of a simple guanidine type base (TBD), are able to transfer the chirality during the isomerization reaction of chiral allylic substrates. In the case of allylic amines, the synthetic utility of the chiral enamine/imine intermediates derived from the isomerization reaction is extensively explored, designing a one-pot protocol for the stereospecific and diastereoselective synthesis of chiral γ-trifluoromethylated aliphatic amines with two non-consecutive stereogenic centers.