ACYLATIONS OF PURINE-6-THIONE AND RELATED COMPOUNDS . A REINVESTIGATION OF SITE OF ACYLATION

Purine-6-thione (1) is acylated on nitrogen, not on sulfur as was previously reported. Thus reaction of 1 with acetic anhydride and with ethyl chloroformate yields, respectively, 9-acetylpurine-6-thione (6) and ethyl purine-6-thione-9-carboxylate (3), as shown by independent syntheses and spectra. 9-Alkylpurine-6-thiones do react with ethyl chloroformate and benzoyl chloride to yield the corresponding S-acyl derivatives. 2-Aminopurine- 6-thione yields ethyl 2-amino-9-carbethoxypurine 6-thiolcarbonate (14). The reaction of 6-chloropurine with ethyl chloroformate, aliphatic acid anhydrides, and benzyl chloroformate gives the corresponding 9-substitution products. 6-Dimethylaminopurine forms a 9-carbethoxy derivative (15). The dipole moments of the 9-benzyl, 7-benzyl, 9-p-nitrobenzyl, and 9-carbethoxy derivatives of 6-chloropurine in dioxane at 20° are 4.91, 5.03, 4.57, and 4.23 D, respectively. © 1969, American Chemical Society. All rights reserved.