REACTIONS OF (E)-O-ARYLBENZALDOXIMES WITH SECONDARY-AMINES IN ACETONITRILE - COMPETITION BETWEEN E2 AND SNAR REACTIONS

Reactions of (E)-O-arylbenzaldoximes in which the O-aryl group is 2,4-dinitrophenyl (1) and picryl (2) with secondary amines in acetonitrile have been studied kinetically. The reactions proceed via competing E2 and S(N)Ar mechanism. The second rate-determining step of the S(N)Ar reactions involves both uncatalyzed and base-catalyzed pathways. The sensitivity of the S(N)Ar reaction to base catalysis was greater for 2 and increased with base strength. The rates of E2 and S(N)Ar reactions increased by approximately 10(3) and 10(4) fold, respectively, with the variation of the substrate from 1 to 2. The yield of S(N)Ar product increased with base concentration, electron-withdrawing ability of O-aryl group, and base strength. From these results, factors that influence the competition between E2 and S(N)Ar reaction pathways are assessed.