Abstract
The development of a Pd(ii)-catalysed enantioselective fluorination of C(sp3)−H bonds would offer a new approach to making chiral organofluorines. However, such a strategy is particularly challenging because of the difficulty in differentiating prochiral C(sp3)−H bonds through Pd(ii)-insertion, as well as the sluggish reductive elimination involving Pd−F bonds. Here, we report the development of a Pd(ii)-catalysed enantioselective C(sp3)−H fluorination using a chiral transient directing group strategy. In this work, a bulky, amino amide transient directing group was developed to control the stereochemistry of the C−H insertion step and selectively promote the C(sp3)−F reductive elimination pathway from the Pd(iv)–F intermediate. Stereochemical analysis revealed that while the desired C(sp3)−F formation proceeds via an inner-sphere pathway with retention of configuration, the undesired C(sp3)−O formation occurs through an SN2-type mechanism. Elucidation of the dual mechanism allows us to rationalize the profound ligand effect on controlling reductive elimination selectivity from high-valent Pd species.
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Acknowledgements
The authors acknowledge financial support from The Scripps Research Institute, the National Institutes of Health (NIGMS, 2R01GM084019) and Shanghai RAAS Blood Products Co. H.P. thanks the Korea Foundation for Advanced Studies and Eli Lilly for graduate fellowship.
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H.P. developed the enantioselective fluorination reaction. H.P. and K.H. expanded the substrate scope. P.V. conducted the computational studies. J.-Q.Y. conceived and supervised the project.
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Supplementary experimental data, synthetic procedures and chemical compound characterization data
Crystallographic data
CIF for compound 5a; CCDC reference: 1556389
Crystallographic data
CIF for compound 6; CCDC reference: 1556390
Crystallographic data
CIF for compound 8; CCDC reference: 1577327
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Park, H., Verma, P., Hong, K. et al. Controlling Pd(iv) reductive elimination pathways enables Pd(ii)-catalysed enantioselective C(sp3)−H fluorination. Nature Chem 10, 755–762 (2018). https://doi.org/10.1038/s41557-018-0048-1
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DOI: https://doi.org/10.1038/s41557-018-0048-1
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