2- Substituted thieno pyrimidin-4 thiones

Cycloaddition and cyclization routes were used to access certain 1,3-diazines. The 4+2 cycloaddition reaction of 4-(N-allyl-N-aryl)amino-l,3-diaza-l,3-butadienes with vinyl-, isopropenyl-, and chloroketene led to pyrimidinone-fused pyrimidinones <97T13841>. Cis-cyclopenta[d]pyrimidines were derived from cis-2-amino-l-cyclopentanecarboxylates by cyclization with KOCN and KSCN <97JHC1211>. 2-Thioxopyrido[3, 2 4,5]thieno[3,2-r/]pyrimidin-4(3//)-ones 19 were prepared by cyclocondensation of 2-carbethoxy-3-amino-4-phenyl-6-substituted-thieno[2,3-/)]pyridines and isothiocyanates <97JHC937>. Thiazolyl-benzimidazoles derived from 2-cyanomethyl-l//-benzimidazole and 2,3-dihydrothiazole-2-(3//)-thiones were cyclized to the corresponding thiazolo[4,5-r/]pyrimidines <97PHA346>. Reductive cyclization of 6-cyanomethyl-5-nitropyrimidines afforded 7-alkyl-5//-pyrrolo[3,2-r/]pyrimidines and 6-amino-7,7-dialkyl-7//-pyrrolo[3,2-rf]pyrimidines <97T391>. 7-Methyl-5-alkyl-2-vinyl-pyrazolo[3,4-r/]pyrimidine-4,6(5//,7//)-diones arose from cyclization and alkylation of... 

Surprisingly, only one example of the synthesis of thieno[3,4-,7 pyrimidines has been described starting from a pyrimidine ring. In CHEC-II(1996) <1996CHEC-II(7)229>, substituted 5-cyanouracils, upon reaction with elemental sulfur, led to the formation of compounds in this class. Now the use of a 5-cyanopyrimidino-2-thione 419 under similar conditions (Equation 156) leads to the thienopyrimidine 420 <1997HC0151>. 

Heating compound 299 with phosphorus pentasulfide in a mixture of dioxane and pyridine gave 7-(2,3,5-tri-0-benzoyI-/3-D-ribofuranosyl) thieno[3,4-d]pyrimidin-4(3//)-thione 374, in 49% yield. Thione 375, obtained by debenzoylating compound 374, was converted into the 4-methyl-thio-7-/3-D-ribofuranosylthieno[3,4-d]pyrimidine 376 by reaction with excess methyl iodide in 0.1 N aqueous sodium hydroxide. Substitution of the... 

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