Heterocyclic ambident nucleophiles. IV. The alkylation of metal salts of adenine

Abstract

The N3 : N7 : N9 alkylation patterns for reactions of the lithium, sodium, and potassium salts of adenine with various alkylating agents in dimethyl sulfoxide were determined by ¹H n.m.r. spectroscopy. Only for the Li⁺ salt was any significant effect of ionic association noticed. Of the alkylating agents used, only chloromethyl pivalate gave a concentration dependent alkylation pattern. The latter effect was most pronounced with the heterogeneous alkylation conditions of anhydrous Na₂CO₃/HCONMe₂, adenine, and chloromethyl pivalate; here, increasing concentrations changed the main reaction from N7- to N9-alkylation. Solvent effects on the alkylation patterns were also studied. Within the common dipolar aprotic solvent group, (Me₂N)₃PO, HCONMe₂ and Me₂SO, effects were small; in protic solvents, particularly formamide, enhanced N3-alkylation was observed.