Pyrimidine-2-thione, reaction with acetate

The 3-imino group of 4-cyano-2-ethyl-3-imino-2,3,5,6,7,8-hexahydro-l//-pyrido[l,2-c]pyrimidine-l-thione was acylated with phenyl isocyanate (78MI1). The imino group of l-imino-4-cyano-3-methylthio-l//-pyrido[l,2-cjpyrimidine was alkylated and acylated with methyl iodide and acetic anhydride (75YZ13). Reaction of 3-amino-4-phenyl-4-[2-(A, N-di-n-pro-pylamino)ethyl-4,4 a,5,6,7,8-hexahydro-l //-pyrido[l, 2-c ]pyri midin-l-one with acetic anhydride in pyridine and with sodium nitrite in aqueous acetic acid afforded 3-acetamido and perhydro-l,3-dioxo derivatives, respectively (87USP4680295). 

Oxidative desulfurization can be effected by ozonolysis (Scheme 74). 2-Thiol-4(3//)-quinazolinone on ozonolysis in dry dichloromethane yields the disulfide (448) which is resistant to further oxidation under the reaction conditions. In acetic acid, desulfurization results with hydrogen substitution (449). Rationalization of the reaction in acetic acid involves formation of an unstable sulfinic acid which loses SO2 with replacement by hydrogen. In dichloromethane containing ethanol, the 2-ethoxy product (450) formed, corresponding to nucleophilic substitution of the reactive sulfinic acid from the oxidation. Similarly, ozonolysis of pyrimidine-2-thione acid gave bis-2-pyrimidinyl disulfide in dry dichloromethane and 2-ethoxypyrimidine in the presence of ethanol <93TL1631>. 

Thiazolo-[4,5-d]- and -[5,4-d]-pyrimidines [C3NS-C4N2]. The reaction of the A" -thiazoline (139) with NaSH or with H2S and pyridine gives the thiazolo-[4,5-i/]pyrimidine-7-thione (140 R = Ac, R = H, X = S), and with acetic anhydride and PPA yields (140 R = H, R = Me,X = O), whilst the readily available ethyl 2-methylmercapto-5-aminothiazole-4-carboxylate will react with formamide to give the thiazolo[5,4- f]pyrimidin-4-one (141). ... 

Deamination of 3-amino derivative 23 with sodium nitrile in acetic acid gave 5,6-dimethylthieno[2,3-d]pyrimidin-4(3//)-one [85IJC(B)432]. Using the same reaction procedure, 3-amino derivative 82b (R = NH2) was converted into the thieno[2,3-d]pyrimidine-2(l//)-thione 78b (90JHC269). 

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