Reactivity-Selectivity Relationships in Reactions of Ambident Nucleophiles with the Superelectrophiles 4,6-Dinitrobenzofuroxan and 4,6-Dinitro-2-(2',4',6'-trinitrophenyl)benzotriazole 1-Oxide

Article abstract of DOI:10.1021/jo00380a003

The reactions of 4,6-dinitrobenzofuroxan (1) and 4,6-dinitro-2-(2',4',6'-trinitrophenyl)benzotriazole 1-oxide (2) with aryl oxides and arylamines have been investigated.Phenoxide ion reacted with 1 to give a carbon-bonded adduct by reaction at C-7, but in contrast with the 1,3,5-trinitrobenzene (TNB) system, aniline reacted to give both nitrogen- and carbon-bonded adducts as observable species, depending on the reaction conditions.Reaction of 2 with phenoxide ion gave products arising solely from nucleophilic attack at C-1' of the picryl moiety.Reaction of 2 with aniline also yielded a nitrogen-bonded adduct when carried out in the presence of 1 equiv of triethylamine as catalyst.Inhibiting the reactivity of aniline through ortho or N-methyl substitution resulted in the formation of C-7 carbon-bonded adducts of 2.These reactions generally involve kinetically preferred but reversible formation of a ? complex that is bonded via the heteroatom, followed by conversion to a carbon-bonded product of thermodynamic control.The extent to which the kinetically and thermodynamically preferred products can be observed is rationalized according to reactivity-selectivity arguments.The formation of carbon-bonded aniline complexes with 1, but not with TNB, is a result of the greater reactivity of the former (a superelectrophile).The observed regiochemistry in the reaction of nucleophiles with 2 depends on the stability of the adduct at the benzotriazole moiety (C-7) and the selectivity of the nucleophile for reaction at the benzotriazole (C-7) vs. the picryl moiety (C-1').Decreased selectivity will result from an increase in thermodynamic driving force for the addition reaction (more negative ΔG₀) and/or, for exergonic reactions, a decrease in intrinsic barrier (i.e., decreased ΔG₀(excit.)).Decreased selectivity resulting from decreased intrinsic barriers will favor rapid formation of the products of thermodynamic control.Previous results with related systems are also rationalized on the basis of stability-selectivity relationships.