Synthese und Eigenschaften von Thiazolo[3,2-a]pyrimidinen und Thiazolo [3,2-a] pyrrolo [2,3-d]pyrimidinen

From the alkali-catalysed reaction of thiouracil with bromoacetaldehyde diethyl acetal three products are isolated in nearly the same quantity: 2-(2, 2-diethoxyethylthio)-uracil ( 2 ) and two cyclization products: 3 , a thiazolo3, 2-a]pyrimidin-5-one, and 4 , athiazolo3, 2-a]pyrimidin7-one. By warming with acid both 2 and 4 yield 3 . Rearrangement of 4 to 3 proceeds also by heating the hydrochloride. Similar cyclizations leading to thiazolo3, 2-d]pyrrolo2, 3-d]pyrimidin-5-ones are also described. Bromine substitutes 3 in position 6. The bromo derivative 6 on treatment with primary or secondary amines affords 7-amino compounds.