From Thioamides for Pyrimidin-4-thiones

4- thione.127 The 5,6-diphenyl analog of this pyrazine behaved similarly, as did the 3-(JV-butyl) derivative of the latter.229 

Examples in which the 2-position of the annelated pyrimidine is substituted include the following. 2-Aminopyrazine-3-thiocarboxamide and trifluoro-acetamide, boiled in ethanolic sodium ethoxide for 8 hr, produced a good yield of 4-mercapto-2-trifluoromethylpteridine (the HS— nature of the sulfur substituent was verified by 1H NMR)213 fusion of 4-aminoimidazole- 

Finally, 2-aminothiobenzamide and acetone, in boiling 1 N hydrochloric acid, furnished an excellent yield of 2,2-dimethyl-l,2-dihydroquinazoline-4-thione (see l).276 

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