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

Abstract

Elimination reactions of N-alkyl-N-chlorothenylamines 1-4 with MeONa-MeOH and Et(2)NH-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 rho 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 Et(2)NH-MeCN. The transition state structure changes toward more product-like as the base is changed from MeONa-MeOH to Et(2)NH-MeCN. Comparison with existing data reveals that the structure of the transition state is relatively insensitive to the beta-aryl group variation.