(5R)-3-Isopropyl-5-phenyl-5,6-dihydro-2H-1,4-oxazin-2-one → (3S,5R)-3-Isopropyl-5-phenyl-3,4,5,6-tetrahydro-2H-1,4-oxazin-2-one

Participants

Reaction Steps

To a solution of (5R)-3-isopropyl-5-phenyl-5,6-dihydro-2H-1,4-oxazin-2-one (38) (1.03 g, 4.74 mmol, 1.0 equiv.) in anhydrous dichloromethane (50 mL) under an atmosphere of nitrogen was added PtO2 (103 mg, 0.1 equiv.). The mixture was consecutively degassed and purged three times with hydrogen and then stirred for 5 hours under an atmosphere of hydrogen. Filtration through a short pad of CELITE® diatomaceous earth and removal of solvent from the filtrate in vacuo yielded the crude product which was purified by flash column chromatography on silica eluting with petrol and diethyl ether (4:1) to furnish the title product as a waxy solid (662 mg, 64%); m.p. 61.5-62.5° C.; v(max)(KBr) 3326 (N—H—), 2960 (C—H), 1733 (C═O), cm−1; δH (250 MHz, CDCl3) 7.47-7.35 (5H, m, Ph); 4.33-4.18 (3H, m, PhCHCH2), 3.81 (1H, m, NHCH), 2.49, (1H, m, CH(CH3)2), 1.68 (1H, br, NH), 1.09 (3H, dd, J 6.75 Hz, CH(CH3)2×3), 1.05 (3H, dd, J 6.75, CH(CH3)2×3); δc, (62.5 MHz, CDCl3) 170.3, 138.5, 129.3, 129.1, 127.6, 74.9, 64.2, 57.3, 32.0, 19.4, 17.4; m/z (Cl, NH3), 237 (MNH4+, 5%), 220 (100%, MH+), 219 (22%), and 216 (6%); HRMS for C13H18NO2 requires 220.1333 found 220.1338. [α]D20 −92.1 (c 1.45 CHCl3).

Provenance & Evidence