Treatment of 9-methyladenine and hydroxyl-protected derivatives of adenosine and 2’-deoxyadenosine with 1,2-bis[(dimethylamino)methylene] hydrazine and/or its dihydrochloride at elevated temperatures in appropriate solvents resulted in elaboration of the 6-amino group into a 6-(1,2,4-triazol-4-yl) substituent in excellent yields. Analogous functionalization of the amino groups of tubercidin {4-amino-7-(beta-D-ribofuranosyl)pyrrolo[2,3-d]-pyrimidine} and formycin {7-amino-3-(beta-D-ribofuranosyl)pyrazolo[4,3-d]pyrimidine} gave the respective 4- and 7-(1,2,4-triazol-4-yl) derivatives. Nucleophilic replacement of the triazole moiety gave the respective 6-, 4-, and 7-substituted purine, pyrrolo[2,3-d]pyrimidine, and pyrazolo[4,3-d]pyrimidine products. This first general method for "direct" nucleophilic replacement of an amino group on these nitrogen heterocycles also provides a new class of compounds for potential postsynthetic modifications after incorporation into oligonucleotides.