N-(Arylthio)benzimidazoles. Torsional Barriers and 1,3-Rearrangement

Article abstract of DOI:10.1021/jo00213a001

A series of N-<(2,4-dinitrophenyl)thio>benzimidazoles has been prepared by reaction of 2,4-dinitrobenzenesulfenyl chloride with a series of 2-alkylbenzimidazoles and 5(6)-chloro-2-alkylbenzimidazoles.Dynamic NMR spectroscopy was used to measure the torsional barriers about the N-S bonds, which were in the range of ca. 19-20 kcal/mol.In one case, diastereomeric transformation and conventional kinetics were used to obtain an independent measure of the torsional barrier.The kinetics of 1,3 rearrangement of the arylthio group from one nitrogen to another suggested that the rearrangement proceeds via a bimolecular mechanism.