Effect of Solvents on Acid-Catalyzed Claisen Amino Rearrangement in N-(1-Methyl-2-butenyl)aniline

The effect solvents have on the processes of rearrangement and elimination in N -(1-methyl-2-butenyl)aniline ( I ) in the presence of HCl is studied. It is shown that the dependence of the rearrangement and elimination rate constants of ( I ) · HCl on the nature of solvents are described perfectly by the Koppel–Palm equation, which considers both nonspecific and specific solvation. The inhibitory effect of solvent nucleophilicity is explained by the complexation between ( I ) · HCl and solvent molecules. Analysis of the ( I ) · HCl conversion products obtained in a mixed solvent ( m -toluidine + nitrobenzene) demonstrates the intermolecular transfer of the allyl moiety, confirming the formation of allyl cations in the Claisen amino rearrangement.