The Orton rearrangement in aprotic solvents. Part IV. An examination of the kinetics of the rearrangement of N-bromo-4-chloroacetanilide and N-bromoacetanilide catalyzed by trifluoroacetic acid and trifluoroacetic acid-d

Abstract

Can. J. Chem. 59,839 (1981). The rates of rearrangement of N-bromo-4-chloroacetanilide to 2-bromo-4-chloroacetanilide catalyzed by trifluoroacetic acid and trifluoroacetic acid-d have been measured as a function of acid concentration in chlorobenzene at T = 323 K. Similar experiments have been carried out with N-bromoacetanilide and N-bromo-4-chloro-2,6-dideuterioacetanilide. A comprehensive analysis of the observed rates for each substrate as a function of acid concentration reveals that the rearrangements involve at least three mechanistic steps when trifluoroacetic acid is the catalyst. In contrast, the rate of rearrangement of N-bromoacetanilide catalyzed by trichloroacetic acid at T = 288 K appears to follow a limiting form of the same rate law. Earlier observations are assessed in the light of the proposed mechanism, and it is concluded that both present and past work can be satisfactorily rationalized in terms of an intramolecular migration of bromine.

Synthesis and reactions of N-(azulen-1-ylmethylene)arylamines †

“…The second step, (2), could be the migration of chlorine from the nitrogen atom to position 4Ј (for 5a and 12) or, when C4Ј is substituted with CH 3 or OCH 3 , to the ortho position of these substituents (for 5c and 5d), similar to the displacement in the Orton rearrangement. 13 The same mechanism can explain the difference between the reactivity of the compounds substituted at C3, 8 and 11. Despite the similar net charge at C4Ј (Scheme 5) for these compounds and for the parent compound 5a, the difference between this parameter at the nitrogen atoms can influence the reactivity of the Schiff bases that decreases in the order: 5a, 8 and 11.…”

“…The pure Schiff bases obtained were, generally, dark-green coloured crystals. The melting points are reported in Table 1 and the elemental analysis, 1 H-, 13 C-NMR, IR and UV-Vis spectra are described in the ESI. † A typical example of the properties of the Schiff bases is described.…”