The 3-N-oxides of 6-chloro- and 6-bromopurine were prepared by halogenation of 6-mercaptopurine 3-oxide and 6-iodopurine 3-oxide from the chloro derivative and HI. Displacement of chloride from 6-chloropurine 3-oxide gave purine-6-sulfonate 3-oxide and 6-methoxypurine 3-oxide. Ethanolic hydroxylamine and 6 methylmercaptopurine 3-oxide led to hypoxanthine 3-oxide. Treatment of 6-chloropurine 3-oxide with NH3, NH2NH2, NH2OH, and morpholine resulted in substitution and simultaneous loss of oxygen to yield adenine and 6-hydrazino-, 6-hydroxylamino-, and 6-morpholinopurine, respectively. Oxidation of 6-mercaptopurine 3-oxide with butyl nitrite afforded its disulfide. 6-Iodopurine 3-oxide inhibited slightly the growth of carcinoma E0771 in mice; the other compounds were inactive. © 1969, American Chemical Society. All rights reserved.