Elimination Reactions of N-Alkyl-N-chlorothenylamines Promoted by MeONa−MeOH and Et2NH−MeCN. Effect of the β-Aryl Group on the Imine-Forming Transition State

Elimination reactions of N-alkyl-N-chlorothenylamines 1−4 with MeONa−MeOH and Et2NH−MeCN have been studied kinetically. The elimination reactions are regiospecific, producing only the conjugated imines. The reactions are second order and exhibit substantial values of Hammett ρ and k H/k D, and an E2 mechanism is evident. The relative rates of elimination for Me/Et/i-Pr/t-Bu substituents are 1/0.5/0.2/0.02 with MeONa−MeOH and 1/0.4/0.2/0.06 with Et2NH−MeCN. The transition state structure changes toward more product-like as the base is changed from MeONa−MeOH to Et2NH−MeCN. Comparison with existing data reveals that the structure of the transition state is relatively insensitive to the β-aryl group variation.