Reactivity of 6-methylthiopurin-8-ones. Properties of 6-methylsulphonylpurin-8-ones

Abstract

All 6-methylthiopurin-8-ones (except those bearing a 1-methyl substituent, which decompose) are converted by chlorine in methanol at 0° into the corresponding sulphones. In a series of N-methyl 6-methylthiopurin-8-ones, only the 1-methyl, the 1,9- and 3,9-dimethyl, and the 3,7,9-trimethyl derivatives undergo thiohydrolysis. In contrast, all the corresponding sulphones are attacked by hydrogen sulphide anion. A 6-methylsulphonyl substituent weakens basicity and increases the acid strength of purines. In 6-methylsulphonylpurin-8-one, anion formation follows the order N-9 → N-7. A 3-methyl substituent, by virtue of reduction of the ring current in the pyrimidine system, causes a diamagnetic shift of the 2-H signal.