Cyclopropylamine → 3-Benzyloxy-1-cyclopropyl-6-methyl-4-oxo-1,4-dihydro-pyridine-2-carboxylic acid

Participants

Reaction Steps

To a suspension of 3-(benzyloxy)-6-methyl-4-oxo-4H-pyran-2-carboxylic acid (70 g, 0.27 mol) in MeOH (350 mL) in a 3-necked RBF (round bottom flask) fitted with a mechanical stirrer was added cyclopropylamine (120 mL, 1.72 mol). A clear light yellow solution resulted. The reaction mixture was refluxed for ca. 19 h. Volatiles were removed in vacuo and the residue was dissolved in water (700 mL) with stirring. The aqueous mixture was filtered through a pad of Celite®. The filtrate was placed in a 3-necked RBF fitted with a mechanical stirrer, and cooled in an ice bath. Conc. HCl was added until the pH was ca. 1-2, and voluminous “orange” solid precipitated out. Acetone (200 mL) was added to the suspension. The solid was then collected by suction filtration, thoroughly washed with acetone, and air-dried. The title compound was obtained as an off-white solid (71.0 g, 88%). Mp: 139.0-139.5° C.; 1H-NMR (300 MHz, DMSO-D6) δ (ppm): 0.98-1.15 (m, 4H, 2 c-CH2), [2.37 (s)+2.40 (s), rotamers, 3/2 ratio, 3H, CH3)], 3.30-3.50 (m, 1H, c-CH), 5.00-5.05 (m, 2H, CH2Ph), 6.20-6.25 (m, 1H, C═CH), 7.28-7.50 (m, 5H, Ph); MS (m/z): 300.2 (M++1), 256.2, 192.2, 164.4, 91.0 (100%); Anal. Calcd. for C17H17NO4: C, 68.21; H, 5.72; N, 4.68%. Found: C, 67.76; H, 5.76; N, 4.61%.

Provenance & Evidence