Unprecedented temperature-dependent formation of 3- and 7-methyl-3H-azepine derivatives by the reaction of o-nitrotoluene with tributylphosphine in nucleophilic media

The reaction of o-methylphenylnitrene in the presence of alcohol and amine was expected to give isomeric pairs of 3- and 7-methyl-3H-azepine derivatives. The formation ratio between these isomers was found to be obviously influenced by reaction temperature, that is, reaction at 150°C gave 7-methyl-3Hazepine derivative, however, it became minor under 70°C in both media. The ratio between 3- and 7-methyl derivatives is explained by a scheme of kinetic- and thermodynamiccontrolled product distribution from o-methylphenylnitrene to 3- and 7-methyldehydroazepine intermediates which are trapped by nucleophilic media to give 3- and 7-methyl-3H-azepine derivatives.