Triazolo purin-9-ones, preparation

Their preparations copied those of their [ ]-analogues. The first method started from 2-hydrazinopurines 287 and suitable ortho esters yielding [l,2,4]triazolo-[4,3- ]purin-9-ones 288 (R2 = Aik, Aryl). Substitution of ortho esters by carbon disulfide led to 7-mercapto-derivative 288 (R2 = SH). The 7-aryl-derivatives were better accessible by the second method—the oxidative cyclization of 2-arylidenehydrazino)-derivatives 289, such as heating with diethyl azodicarboxylate, or oxidation with aerial oxygen (85CPB3113) (Scheme 82). 

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