3,4-Dihydro-2H-pyrido[1,2-a]pyrimidin-2-one

3,4-Dihydro-2h-pyrido[1,2-a]pyrimidin-2-one is prepared by reaction of 2-aminopyridine with either Acrylic Acid itself or an  equivalent (2-bromo- or 2-iodopropionic acid, Methyl Acrylate, ethyl 2-bromopropionate, β- Propiolactone).

The reagent may be dried over P2O5 in vacuo (135 °C/17 mmHg).

Dissolve it in CHCl3, filter, evaporate, then recrystallise the residue from EtOH/Me2CO (needles) which can be washed with Et2O and dried. It can also be recrystallised from CHCl3/pet ether or CHCl3/hexane. The hydrochloride has m 295-295o (dec, from EtOH or MeOH/Et2O), the hydrobromide has m 299-300o(dec) (from MeOH/Et2O) and the picrate has m 224-226o(corr), m 219-220o from EtOH. [Adams & Pachter J Am Chem Soc 74 4906 1952, Lappin J Org Chem 23 1358 1958, Hurd & Hayao J Am Chem Soc 77 115 1955, Beilstein 24 III/IV 299.]