Reactions of (E)-O-arylbenzaldoximes in which the O-aryl group is 2,4-dinitrophenyl (1a–d) and picryl (2a–d) with secondary amines in acetonitrile have been studied kinetically. The reactions proceeded via competing E2 and SNAr mechanisms. For eliminations from la–d promoted by R2NH in MeCN, the transition state was changed toward Elcb-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 SNAr reactions of all substrates were relatively insensitive to the variation of either β-aryl substituent or base strength. The yield of SNAr product increased with base concentration, electron-withdrawing ability of the O-aryl group, and base strength. When the electron-withdrawing ability of the β-aryl substituent is increased, the yield of SNAr product from 1a–d decreased, although no clear trend was observed for 2a–d. From these results, factors that influence the competition between E2 and SNAr reaction pathways are assessed.
ASJC Scopus subject areas
- Organic Chemistry