Aromatic Nucleophilic Substitution. XIII. Confirmation of the Anionic σ Complexes in the Reactions of 2,4-Dinitro- and 2,4,5-Trinitro-1-(1-piperidyl)naphthalenes with Piperidine in Dimethyl Sulfoxide

Abstract In the reactions of 2,4-dinitro- and 2,4,5-trinitro-1-(1-piperidyl)naphthalenes with piperidine in dimethyl sulfoxide, the 1,1-disubstituted anionic σ complex was confirmed to exist with visible absorption and NMR spectra. Especially in the latter case the 1,3-disubstituted anionic σ complex was formed, the cause of formation of which was ascribed to the deactivating effect of 1-piperidyl group on C1-position of a napthtalene ring and the steric effect of 1-piperidyl group on the nucleophilic attack of piperidine on C1-position. These factors make the 1,1-disubstituted anionic a complex unstable.