Phenyl isocyanate → 7a-(3-benzyl-5-isoxazolyl)-hexahydro-1H-pyrrolizine

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2-Phenylnitroethane (895 mg, 5.92 mmol, from step 15b) and phenylisocyanate (1.3 mL, 11.8 mmol) were dissolved in benzene (12 mL) and added to a flask containing 7a-ethynyl-hexahydro-1H-pyrrolizine (400 mg, 2.96 mmol, from step 13a). The solution was stirred at reflux for 5 hours, cooled and stirred for 48 hours at room temperature. The mixture was filtered and extracted with 6N HCl. The aqueous phase was made basic with 15% NaOH and extracted with methylene chloride. The organic extracts were combined, dried (MgSO4) and concentrated. The residue was chromatographed (silica gel; CHCl3 /MeOH, 99:1) to afford an amber oil (415 mg, 52%). 1H NMR (CDCl3, 300 MHz) δ1.71-1.92 (m, 6H), 2.11-2.23 (m, 2H), 2.58-2.66 (m, 2H), 3.08-3.15 (m, 2H), 3.95 (s, 2H), 5.87 (s, 1H), 7.20-7.34 (m, 5H); MS (CI/NH3) m/z: 269 (M+H)+.

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