OZONATION OF CAFFEINE IN AQUEOUS-SOLUTION

Caffeine (1, 3, 7-trimethylxanthine), a component of waste water, produces numerous rearranged products upon ozonation. These products include dimethylparabanic acid (2), 1, 3-dimethyloxonic methylamide (3), 1, 3-dimethyl-5-azabarbituric acid (4), methylparabanic acid (5), N, N'-dimethyloxalamide (6), IV-methyloxalamide (7), 1.3- dimethyl-5-azauracil (8), and 1, 3-dimethyl-5-hydroxyhydantoin (9). The ozonation of l-ethyl-3, 7-dimethylxanthine (12) and 1, 3-dimethyl-7-ethylxanthine (13) yield product mixtures similar to those from caffeine (1). The production of ethylated oxonic acid derivatives allows the elucidation of a mechanistic pathway for 1.3- dimethyloxonic methylamide (3) formation from caffeine (1). The ozonation of trideuteriomethyl-labeled caffeine analogues demonstrates that 86% dimethylparabanic acid (2) results from the pyrimidine ring of caffeine (1), the rest involving the imidazole ring. The ozonation of 1, 3-dimethyluracil (25) produces dimethylparabanic acid (2) and 1, 3-dimethyl-5-hydroxyhydantoin (9). The latter compound retains C-5 and expels C-6 as demonstrated by ozonation of deuterium-labeled starting material. The ozonation of 1, 3, 5-trimethyluracil (28) produces N-znethylpyruvamide (29) and l, 3, 5-trimethyl-5-hydroxyhydantoin (30). The data obtained permit the proposal of reasonable mechanisms for the formation of the major products. © 1979, American Chemical Society. All rights reserved.