5-Methyl-3H-pyrazol-3-one

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a solution of 3-methyl-pyrazol-5-one (5.7 g, 58.0 mmol) in anhydrous 1,4-dioxane was added 3-bromopropionic acid, and the resulting mixture was heated to reflux for 48 h.12 The reaction mixture was concentrated under reduced pressure, and the crude product was purified by column chromotography using 5-10% MeOH/DCM as an eluent to give 3j (22%) as a solid.13 mp: 210-215° C. (Lit. mp 178-180° C.); 1H NMR (400 MHz, CDCl3): δ 2.21 (s, 3H), 2.76 (m, 2H), 3.14 (s, 2H), 4.14 (m, 2H), 8.01 (brs, 1H); HRMS (m/z): [M−H]− calcd for C7H4N2O3, 169.0619; found, 169.0622. the resulting mixture was heated to reflux for 48 h 12 The reaction mixture was concentrated under reduced pressure the crude product was purified by column chromotography