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Suzuki–Miyaura Cross‐Coupling Reactions of Highly Fluorinated Arylboronic Esters: Catalytic Studies and Stoichiometric Model Reactions on the Transmetallation Step

DOI

26

Citations

145

References

2017

Year

Johannes Kohlmann, Thomas Braun, Reik Laubenstein, Roy Herrmann
Chemistry - A European Journal

Abstract

Fluorinated 4-aryl phenylalanine amino acid derivatives (aryl=2-C<sub>5</sub> NF<sub>4</sub> , 4-C<sub>6</sub> H<sub>4</sub> SF<sub>5</sub> , 2-C<sub>6</sub> H<sub>4</sub> SCF<sub>3</sub> , C<sub>6</sub> F<sub>5</sub> ) were obtained in Suzuki-Miyaura cross-coupling reactions of phenylalanine precursors with highly fluorinated aryl boronic acid and esters in the presence of CsF. Pd<sup>II</sup> complexes that possessed phenyl alanine derived ligands, such as trans-[PdBr{4-C<sub>6</sub> H<sub>4</sub> CH<sub>2</sub> CH{NHC(O)CH<sub>3</sub> }CO<sub>2</sub> Et}(PiPr<sub>3</sub> )<sub>2</sub> ], were used as catalysts. Stoichiometric model reactions indicate the intermediate generation of the boronate Cs[BF(2-C<sub>5</sub> NF<sub>4</sub> )(pin)] (pin=pinacolato=O<sub>2</sub> C<sub>2</sub> Me<sub>4</sub> ). The transmetallation step with Cs[BF(4-C<sub>6</sub> H<sub>4</sub> SF<sub>5</sub> )(pin)], [NMe<sub>4</sub> ][BF(2-C<sub>5</sub> NF<sub>4</sub> )(pin)] and/or the fluorido complex trans-[PdF{4-C<sub>6</sub> H<sub>4</sub> CH<sub>2</sub> C{NHC(O)CH<sub>3</sub> }(CO<sub>2</sub> Et)<sub>2</sub> }(PiPr<sub>3</sub> )<sub>2</sub> ] was investigated. A comparison of the reactions of trans-[PdX{4-C<sub>6</sub> H<sub>4</sub> CH<sub>2</sub> C{NHC(O)CH<sub>3</sub> }(CO<sub>2</sub> Et)<sub>2</sub> }(PiPr<sub>3</sub> )<sub>2</sub> ] (X=Br, F) with 2-Bpin-C<sub>5</sub> NF<sub>4</sub> or [NMe<sub>4</sub> ][BF(2-C<sub>5</sub> NF<sub>4</sub> )(pin)] revealed the remarkable high reactivity of the fluorido complex towards 2-BpinC<sub>5</sub> NF<sub>4</sub> . Low-temperature NMR studies indicated the ionic species trans-[Pd{4-C<sub>6</sub> H<sub>4</sub> CH<sub>2</sub> C{NHC(O)CH<sub>3</sub> }(CO<sub>2</sub> Et)<sub>2</sub> }(PiPr<sub>3</sub> )<sub>2</sub> ][BF(2-C<sub>5</sub> NF<sub>4</sub> )(pin)] to be a highly reactive intermediate.

References

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