Purines. IV. O→N (9) Alkyl Migration in the Alkylation of 1-Alkoxyadenines

Abstract

Treatment of 1-alkoxyadenine (I) with reactive alkyl halides (R2X) in N, N-dimethylacetamide yielded the 9-alkylated salts (II) in good yields. However, an alkyl halide (R2X) less reactive than that (R1X) whose alkyl group was the same as in I reacted with I to give a mixture of at most four possible 1-alkoxy-9-alkyladenine salts (II, IV, V, and VII), two 9-alkyladenine 1-oxides (III and VI), and, possibly, a more reactive alkyl halide (R1X). The intricate pattern of formation of products was due to O→N (9) alkyl migration during the reaction, and a plausible mechanism is presented. A clear O→N (9) benzyl migration was demonstrated by the reaction of 1-benzyloxyadenine (I: R1=C6H5CH2) with 0.1 equivalent of benzyl bromide to give 0.58 equivalent of 9-benzyladenine 1-oxide (VI: R1=C6H5CH2).