Reactions of N-Halo-N-methylbenzylamines with MeONa-MeOH and t-BuOK—t-BuOH. Effects of /3-Carbon Substituent and Base—Solvent System upon the Imine-Forming Transition State

Elimination reactions of YC₆H₄CH(R)N(X)CH₃in which R = Me and Ph and X = Cl and Br promoted by MeONa-MeOH and t-BuOK—t-BuOH have been studied kinetically. The elimination reactions are regiospecific, producing only the corresponding N-benzylidenemethylamines and are quantitative when X = Cl. Comparison with published data for R = H reveals that with both base-solvent combinations variation of the β-carbon substituent from Me to H to Ph produces an increase in the ρ value, first an increase and then a decrease in k_H/k_D, and a decrease in k_Br/k_cl. When the base-solvent system is changed from MeONa-MeOH to t-BuOK—t-BuOH the ρ value increases, k_H/k_D remains nearly constant, and k_Br/k_cl decreases for all three R groups. From these results, the changes in transition-state structure wrought by variation of the β-carbon substituent and the base-solvent system are assessed.