Hydrochloric Acid → 7-methyl-7-phenyl-6,7-dihydrocyclopenta[e][1,3]oxazine-2,4(3H,5H)-dione

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Combined 2-methyl-2-phenylcyclopentanone (Intermediate V(1) (705.5 mg, 4.05 mmol) and carbonisocyanatidic chloride (1700 mg, 8.06 mmol), flushed with N2, and sealed in a sealed tube. Heated at 58° C. for 1 h, then 130° C. for 1.75 h. Let cool to rt. Carefully opened the tube (HCl), and dissolved the residue in EtOAc. Partitioned with NaHCO3 (aq), and extracted 3 times into EtOAc. Washed combined organic layers with brine, dried over MgSO4, filtered, and concentrated in vacuo. Loaded the residue onto Silica gel and eluted with an EtOAc/Hexane gradient to afford 7-methyl-7-phenyl-6,7-dihydrocyclopenta[e][1,3]oxazine-2,4(3H,5H)-dione (43% yield)LC-MS (M+H)+=244.1. 1H NMR (500 MHz, CDCl3) δ ppm 8.12 (1H, br. s.), 7.32-7.38 (2H, m), 7.26-7.30 (3H, m), 2.69-2.75 (2H, m), 2.43-2.52 (1H, m), 2.21-2.29 (1H, m), 1.68 (3H, s).

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