Reactions of (E)-O-Arylbenzaldoximes with Secondary Amines in Acetonitrile. Effect of β-Aryl Substituents upon the Competition between E2 and SNAr Reactions

Article abstract of DOI:10.1021/jo00075a009

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 S_NAr mechanisms.For eliminations from 1a-d promoted by R2NH 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_NAr reactions of all substrates were relatively insensitive to the variation of either β-aryl substituent or base strength.The yield of S_NAr 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 S_NAr 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 S_NAr reaction pathways are assessed.