Nucleophilic aromatic substitution of the nitro-group

Abstract

The reaction of piperidine with 1,2,4-trinitrobenzene or with o-dinitrobenzene in benzene affords 2,4-dinitro-1-piperidinobenzene or 2-nitro-1-piperidinobenzene, respectively, in quantitative yield. Neither reaction undergoes base catalysis and overall second-order kinetics (first-order with respect to each reagent) were observed for a wide range of piperidine concentrations in benzene. Acid catalysis does not occur either as added p-methoxyphenol fails to affect appreciably the kinetics of the reaction of the trinitrobenzene. Comparison with the reaction of piperidine with 1-fluoro-2,4-dinitrobenzene in benzene, where pronounced catalysis by both piperidine and p-methoxyphenol has been observed, allows an interpretation of the reaction in terms of an addition–elimination mechanism with rapid expulsion of the nitro-group from the intermediate. Why the expulsion of the nitro-group from the intermediate should occur so easily is not clear, however. The recent literature concerning the nucleophilic aromatic substitution of the nitro-group is reviewed.