Acid-Catalyzed Hydrolyses of Acylpyrroles and Acylindoles. Noninvolvement of Protonated Substrates

Article abstract of DOI:10.1021/ja00406a034

The acid hydrolyses of N-(trifluoroacetyl)pyrrole, -indole, and -tetrahydrocarbazole and of N-acetylindole exhibit rate maxima in H2SO4 (20-40 wt percent, -H₀ = 1-2.5) that are not due to exstensive substrate protonation.The reactions have very large ω and φ values, suggesting that there is a large difference in hydration of the initial and transition states.N-(Trifluoroacetyl)pyrrole is hydrated in water, and this evidence and that of hydrogen solvent isotope and salt and acid effects show that acid-catalyzed brekdown of a gem-diol is rate limiting.Rate maxima in acid hydrolyses of other weakly basic substrates can be explained in these terms.