Strain effects in acyl transfer reactions. Part II. The kinetics of aminolysis of some N-aryl-lactams

Abstract

The reactions between aliphatic amines and 1-p-nitrophenylazetidin-2-one (I) show marked general base catalysis while hydroxide ion catalysis becomes dominant at high pH. The effect of strain in the β-lactam is manifest in the overall rate of reaction of piperidine with (I) which is at least 10³ times greater than that with the corresponding γ-lactam (II). The Brønsted coefficient of 1·05 for the uncatalysed reactions of (I) with alkylamines shows that the transition state for these reactions is advanced along the reaction co-ordinate as a result of this ring strain and involves less C–N bond stretching than expected for the aminolysis of unstrained anilides.