How is 3,4-Dihydro-2H-pyrido[1,2-a]pyrimidin-2-one (CAS: 5439-14-5) typically synthesized?

3,4-Dihydro-2H-pyrido[1,2-a]pyrimidin-2-one can be synthesized via multistep reactions involving the condensation of a pyridine derivative with a hydrazine derivative. Common synthesis methods include the condensation of 2-cyano-3,4-dihydro-2H-pyrido[1,2-a]pyrimidin-2-one with hydrazine hydrate in the presence of a catalyst such as hydrochloric acid, followed by dehydration under appropriate conditions to yield the target compound with high selectivity and yield.