From N-(dinitrophenyl) amino acids to benzimidazole N-oxides. Synthesis, kinetics and mechanism

ELBA I. BUJÁN; MARÍA LAURA SALUM

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY

John Wiley & Sons, Ltd

Lugar: I; Año: 2006 vol. 19 p. 187 - 195

0894-3230

Several benzimidazole N-oxide derivatives were synthesized in very good yields by heating under reflux the corresponding N-(2,4- or 2,6-dinitrophenyl) amino acid derivative with NaOH in 60% 1,4-dioxane?H2O. The N-oxides obtained from glycine and - and -alanine derivatives lost the carboxylic group. The observed rate constant for the reaction of N-(2,4-dinitrophenyl) glycine (2a) in 10% 1,4-dioxane?H2O to give 5-nitro-1H-benzimidazole-3-oxide (4a) is first order on [NaOH]; the second-order rate constant is kN¼1.7103 M1 s1. The mechanism proposed includes the formation of an N-alkylidene 2-nitrosoaniline-type intermediate as the rate-determining step.