Kinetics and Mechanism of the Aminolyses of Bis(2-oxo-3-oxazolidinyl) Phosphinic Chloride in Acetonitrile

摘要

The aminolyses, anilinolysis and pyridinolysis, of bis(2-oxo-3-oxazolidinyl) phosphinic chloride (1) have been kinetically investigated in acetonitrile at 55.0 and 35.0 °C, respectively. For the reactions of 1 with substituted anilines and deuterated anilines, a concerted S_N2 mechanism is proposed based on the selectivity parameters and activation parameters. The deuterium kinetic isotope effects (k_H/k_D) invariably increase from secondary inverse to primary normal as the aniline becomes more basic, rationalized by the transition state variation from a backside to a frontside attack. For the pyridinolysis of 1, the authors propose a stepwise mechanism with a rate-limiting step change from bond breaking for more basic pyridines to bond formation for less basic pyridines based on the selectivity parameters and activation parameters. Biphasic concave upward free energy relationship with X is ascribed to a change in the attacking direction of the nucleophile from a frontside attack with more basic pyridines to a backside attack with less basic pyridines.