Reactions of (E)-O-arylbenzaldoximes with secondary amines in acetonitrile. Effect of .beta.-aryl substituents upon the competition between E2 and SNAr reactions

Reactions of (E)-O-arylbenzaldoximes in which the O-aryl group is 2,4-dinitrophenyl (1a-d) and picryl (2a-d) nvith secondary amines in acetonitrile have been studied kinetically. The reactions proceeded via competing E2 and S N Ar mechanisms. For eliminations from 1a-d promoted by R 2 NH in MeCN, the transition state was changed toward E1cb-like by a more electron-withdrawing β-aryl substituent and a stronger base. On the other hand, the transition states for eliminations from 2a-d and for the S N Ar reactions of all substrates were relatively insensitive to the variation of either β-aryl substituent or base strength. The yield of S N Ar product increased with base concentration, electron-withdrawing ability of the O-aryl group, and base strength