Aminolysis of X-Substituted Phenyl Diphenylphosphinates: Effect of Amine Nature on Reactivity and Transition-State Structure

A kinetic study is reported for aminolysis of X-substituted phenyl diphenylphosphinates (1a−i) in 80 mol % H2O/20 mol % dimethyl sulfoxide at 25.0 ± 0.1 °C. The Bronsted-type plot for the reactions of 2,4-dinitrophenyl diphenylphosphinate (1a) with primary amines is linear with βnuc = 0.53. The reactions of 1a−i with ethylamine also result in a linear Bronsted-type plot with βlg = −0.81. These βnuc and βlg values are slightly larger than those reported previously for the reactions of 1a with secondary amines (βnuc = 0.38) and for those of 1a−i with piperidine (βlg = −0.66) but typical for reactions that proceed through a concerted mechanism. It has been concluded that aminolysis of 1a−i proceed through a concerted mechanism and the nature of amines does not affect the reaction mechanism. However, the reactions with primary amines have been suggested to proceed through a later transition state (i.e., more bond formation and bond rupture in the transition state) on the basis of the larger βnuc and βlg value...