Allylic Amination of Pd(II)-Allyl Complexes via High-Valent Pd Intermediates

Abstract

Organometallic high-valent Pd(allyl) complexes have been recently proposed to act as intermediates in catalytic allylic functionalization reactions. While a few Pd IV (η 1 -allyl) complexes have been isolated and characterized, Pd III (η 3 -allyl) or Pd III (η 1 -allyl) complexes have not been detected or isolated to date. Reported herein is the synthesis, characterization, and reactivity of a series of Pd II (η 3 -allyl) complexes supported by the tetradentate pyridinophane ligands N, N′-di-tert-butyl-2,11-diaza-[3.3](2,6)pyridinophane ( tBu N4) and N, N′-di-tert-methyl-2,11diaza[3.3](2,6)pyridinophane ( Me N4). These Pd II (η 3 -allyl) complexes exhibit accessible oxidation potentials and upon oxidation generate Pd III (allyl) complexes that were characterized by electron paramagnetic resonance (EPR) spectroscopy. Interestingly, the [( Me N4)Pd III (η 3 -allyl)] 2+ complex undergoes a rearrangement to the [( Me N4)Pd III (η 1 -allyl)] 2+ species at low temperatures. Moreover, fast allylic amination occurred within 15 min at room temperature upon the reaction of [( Me N4)Pd II (η 3 -allyl)] + complexes with N-fluorobenzenesulfonimide (NFSI), and the C−N bond formation step is proposed to occur at the Pd(IV) oxidation state, likely via a Pd IV (η 1 -allyl) intermediate.

Synthesis of Chiral Tricyclic Pyrone Molecules via Palladium(0)‐Catalyzed Displacement Reactions of Chiral Tricyclic Pyrone Acetate With Azide or Amine

“…However, the yields are solvent dependent along with limited acetate substrates. In addition to displacement of allylic acetates, direct allylic aminations of Pd(II)‐allyl complexes or alkenes were restricted to the use of highly stabilized anion deriving from N ‐fluoro‐dibenzenesulfonimide and KF [13b,c] . Hence, we studied the displacement reactions of allylic acetate 9 with 3‐fluoro‐4‐(aminomethyl)phenol ( 12 ) or 3‐fluoro‐4‐( t ‐butyldimethylsilyloxy)benzylamine ( 13 ) catalyzed by different palladium complexes in the presence of a base, and in different solvents such as DMF, THF or DMPU.…”