Hydrogen Bond-Enhanced Halogen Bonding Organocatalyst with C(sp³)–Br and Sulfoxide Moieties

Neutral halogen bonding donors (XBDs) containing sp3-hybridized carbon–bromine and sulfoxide moieties were designed and synthesized. They promoted quinolines and imines reduction easily with a relatively low catalyst loading (5 mol %). Their halogen bonding strengths were quantified using 31P NMR spectroscopy and molecular electrostatic potential (MESP) analysis. Single-crystal X-ray analysis unambiguously confirmed the presence of intramolecular C(sp3)–Br···H–N hydrogen bonding within the amide-derived XBD. Combined experimental and computational studies revealed that the amide-derived XBD acts as an efficient hydrogen bond-enhanced halogen bonding organocatalyst.