Nucleophilic displacement and spiro-complex formation in NN′-dimethyl-N-picrylethylenediamine

Abstract

Reaction of the title compound as the hydrochloride salt with Et₃N in dimethyl sulphoxide or dimethylformamide solution gave rise rapidly to the spiro-complex (9), followed by slow formation of (12), the product of intramolecular nitro-displacement. When NaOMe in DMSO–MeOH was used as the base, the overall conversion to (12) was much more sluggish. Reactivities in the two systems are discussed and the more facile reaction with Et₃N is suggested to arise mainly as a result of general acid-catalysed ring-opening of (9) by Et₃NH⁺, thus increasing the concentration of free amine, the reactive species in the displacement process. The results tend to rule out alternative mechanisms of nitro-displacement in which the spiro-complex serves as the reactive species in product formation.