Reactions of N-(Arylsulfonoxy)-N-Alkylbenzylamines with Meona-Meoh. Steric Effect on the Structure of the Imine-Forming Transition State

Elimination reactions of N-(arylsulfonoxy)-N-alkylbenzylamines 1–5 with MeONa-MeOH have been studied kinetically. the elimination reactions are regiospecific, producing only corresponding benzylidenalkylamines. the rate equation for the reactions is k_obs, = k₀ + k₂[MeONa], indicating that the reactions proceed by competing solvolytic- and base-promoted pathways. the relative rates of elimination for the k₂ and k₀ pathways are 1, 0.67, 0.53, 0.35, and 0.27 for R = Me, Et, i-Pr, s-Bu, and t-Bu and 1, 4.1, 5.1, and 8.7 for R = Et, i-Pr, s-Bu, and t-Bu, respectively. for MeONa-promoted elimination from 1–5, Hammett ρ and k_H/k_D decrease but ρ_lg and |β_1g| increase with a bulkier alkyl substituent. However, the values for the solvolytic eliminations are nearly the same for all substrates and are similar to those for the base-promoted pathway, except for the ρ values, which have opposite signs. from these results, the changes in transition-state structure wrought by variation of N-alkyl substituents are assessed.