Ligand-accelerated enantioselective methylene C(sp3)–H bond activation

• Autores: Gang Chen, Wei Gong, Zhe Zhuang
• Localización: Science, ISSN 0036-8075, Vol. 353, Nº 6303, 2016, págs. 1024-1027
• Idioma: inglés
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• Resumen

  • Effective differentiation of prochiral carbon–hydrogen (C–H) bonds on a single methylene carbon via asymmetric metal insertion remains a challenge. Here, we report the discovery of chiral acetyl-protected aminoethyl quinoline ligands that enable asymmetric palladium insertion into prochiral C–H bonds on a single methylene carbon center. We apply these palladium complexes to catalytic enantioselective functionalization of β-methylene C–H bonds in aliphatic amides. Using bidentate ligands to accelerate C–H activation of otherwise unreactive monodentate substrates is crucial for outcompeting the background reaction driven by substrate-directed cyclopalladation, thereby avoiding erosion of enantioselectivity. The potential of ligand acceleration in C–H activation is also demonstrated by enantioselective β-C–H arylation of simple carboxylic acids without installing directing groups.