Amidines. Part 39.1 Formation of N1,N1-dialkylamidines in the reaction between amide acetals and substituted anilines in pyridine. Reaction mechanisms

Abstract

The reaction rates of six N,N-dialkylformamide acetals (R¹)₂N–CH(OR²)₂ with a series of anilines substituted on the phenyl ring have been measured in pyridine. The reaction is found to be irreversible and obeys second-order kinetics. Reaction rates are correlated with Hammett σ constants. Based on the plots and a comparison of reaction rate constants it is shown that the reaction proceeds via two mechanisms which differ from that for the reaction in neutral solvents. It is shown that for compounds with weakly basic NH₂ groups the reaction rates in pyridine are markedly higher than in neutral solvents.