Regioselective Synthesis of 7,8-Dihydropyrrolo[1,2-a]pyrimidin-4(6H)-ones and 7,8-Dihydropyrrolo[1,2-a]pyrimidin-2(6H)-ones.

Annulated analogues of 5,6-dihydroxypyrimidine-4-carboxylate ester and 5,6-dihydroxypyrimidine-4-carboxylamide were synthesized. The intermediary homoallylic amines were subjected to a ring-closure reaction under different reaction conditions. A notable pH-dependency of the ring closure leading to regioisomeric tetrahydropyrrolo[1,2-<italic>a</italic>]pyrimidines was observed. Treatment with dimethyldioxirane and base led to 3-hydroxy-4-oxo-4,6,7,8-tetrahydropyrrolo[1,2-<italic>a</italic>]pyrimidines while <italic>m</italic>-chloroperbenzoic acid or NBS afforded 3-hydroxy-2-oxo-2,6,7,8-tetrahydropyrrolo[1,2-<italic>a</italic>]pyrimidines. [ABSTRACT FROM AUTHOR]