Kinetics and mechanism of the aminolysis of dimethyl and methyl phenyl phosphinic chlorides with anilines

The reactions of dimethyl phosphinic chloride ( 1 ) and methyl phenyl phosphinic chloride ( 2 ) with X‐anilines have been studied kinetically in acetonitrile at 15.0 and 55.0 °C, respectively. The deuterium kinetic isotope effects (KIEs) involving deuterated aniline nucleophiles (XC 6 H 4 ND 2 ) are also reported for the same reactions. The obtained KIEs for 1 are secondary inverse ( k H / k D  = 0.703–0.899 < 1), while those for 2 are primary normal ( k H / k D  = 1.62–2.10 > 1). A concerted mechanism involving predominantly backside nucleophilic attack is proposed for the anilinolysis of 1 . A concerted mechanism involving predominantly frontside attack via a hydrogen‐bonded four‐center‐type transition state is proposed for the anilinolysis of 2 . The degree of steric hindrance is the major factor that determines both the reactivity of the phosphinates and the direction of the nucleophilic attack on the phosphinates. Copyright © 2008 John Wiley & Sons, Ltd.