1. in a 350 mL sealed reactor, ethyl 1-benzyl-4-oxopiperidine-3-carboxylate hydrochloride (50.0 g, 0.168 mol), formamidine acetate (16.2 g, 0.201 mol), a methanolic solution of 4.37 M sodium methanolate (190 mL), and methanol (200 mL) were mixed. 2. the reaction mixture was heated to 85 °C and maintained for 16 hours. 3. Upon completion of the reaction, the mixture was cooled and concentrated under reduced pressure.4. The concentrated residue was dissolved in 1 N NaOH solution (150 mL), which was subsequently poured into ice water.5. The pH of the mixture was adjusted to 7 by slow addition of glacial acetic acid, and a tan solid precipitated.6. The solid was collected by filtration, and washed sequentially with water and cold ethyl ether.7. It was dried under high vacuum to afford 6-benzyl-5,6,7,8-tetrahydropyridine and [4,3-d]pyrimidin-4(3H)-one as a brown solid (26.2 g, 61.4% yield). 8. Mass spectrometry showed [M + H]+ = 242.2. 9. 1H NMR (DMSO-d6) δ: 2.29 (t, J = 5.8 Hz, 2H), 2.61 (t, J = 5.8 Hz, 2H), 3.26 (s, 2H), 3.64 (s, 2H), 3.65 (s, 2H), 3.66 (s, 2H), 3.67 (s, 2H), 3.67 (s, 2H). 3.64 (s, 2H), 7.21-7.36 (m, 6H), 7.96 (s, 1H).
![6-benzyl-5,6,7,8-tetrahydropyrido[4,3-d]pyrimidin-4(3H)-one](/CAS/GIF/109229-22-3.gif)