Pyrimidine-4-thiones, 1,2-dihydro synthesis

Russian workers (82KGS118) reported the synthesis of 5,6-dihydro-thieno[2,3-d]pyrimidine 122 by brominating 5-allylpyrimidine-4(3//)-thione 121. 

The preparation of 9-niethyl and 9-butyl-2-hydroxy-8,9-dihydro-7H-purine-8-thione (XXVa Table 7) is somewhat unusual. Brown [45) has obtained these compounds from carbon disulfide and respectively f-methyl and 1 -butyl-5,6-diamino-1,2-dihydropyrimidin-2-one (XXIVa.). Evidently a shift of the alkyl group from the 3-N to the 9 N atom must occur during the ring closure. The structure of these two purines has been confirmed by their independent synthesis from 4-methylamino and 4-butylamino-5-amino-2-hydroxy pyrimidine. 

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