Reactivity‐Tunable Palladium Precatalysts with Favorable Catalytic Properties in Suzuki–Miyaura Cross‐Coupling Reactions

Abstract

AbstractIn this study, two (HO)R2P→Pd(II)Cl2←NHC precatalysts (1 s) were designed and synthesized. Using these precatalysts, unreactive aryl chlorides, benzyl chlorides, or benzoyl chlorides were highly efficiently converted to the desired products in three to tens of minutes at 35 °C. Upon deprotonation of 1 s, density‐functional theory calculations and electrospray ionization mass spectrometry revealed that NHC was dissociated from the deprotonated precatalysts. Although it is difficult to ascertain the NHC dissociated from Pd(II) or Pd(0) species, the proposed anionic (O−)R2P→Pd(II)Cl2 species could be reduced using ethoxide to form Pd(0) catalytic species. The cation and anion functions of salt additives were systematically elucidated. The cation size could be used to modulate the catalytic properties of 1 s through outer‐sphere electrostatic interactions between the coordinated R2P(O−) and alkali metal ions. Moreover, the basicity of base was proportional to the catalytic yields. This study introduces newly designed Pd(II) precatalysts with superb catalytic properties that are stable and remarkably efficient.