Heterocyclic ambident nucleophiles. III. The alkylation of sodium adenide

Abstract

The alkylation of sodium adenide in HCONMe₂ (30º) with various alkylating agents was analysed by ¹H n.m.r. spectroscopy. Widely varying N3 : N7 : N9 alkylation patterns were observed, depending on the alkylating agent. These patterns are interpreted in terms of the electrostatic, thermodynamic and steric factors involved in the different S_N2 transition states appropriate to each alkylating agent. Hydrogen bonding association between the 6-amino group and certain carbonyl containing alkylating agents is proposed to explain the enhanced N7-alkylation in some cases. Support for this latter proposal was obtained from a comparison of the adenine alkylation results with the corresponding alkylation patterns of 6-pivaloylamino- and 6-chloro-purine.