1,5-Diazabicyclo[4.3.0]-5-nonene

Typical procedure (entry 1): In a 50 mL glass round-bottom flask with the Boc-aziridine (1g, 5.07 mmol) is dissolved in methyl tert-butyl ether (MTBE) (5.1 mL). DBN (125.2 micro-L, 1.01 mmol), is charged, followed by HFIP (2.13 mL, 20.3 mmol) and PhCOF (1.12 mL, 10.1 mmol). The flask is sealed and stirred at 50 °C for 1 h, and quenched with 25 mL of 7 M methanolic NH₃. After 3h with stirring, the reaction mixture is poured into 1 M aqueous NaOH (100 mL) and diluted with 20% Et₂O-hexanes (35 mL). The organic layer is washed with 1 M NaOH (2 ×), and the aqueous layer is extracted with 20% Et₂O-hexanes (15 mL). The combined organic extracts are stirred vigorously over MgSO₄ and SiO₂, filtered, and concentrated. The desired tert-butyl (trans-2-fluorocyclohexyl)carbamate is obtained as a white solid (1.01 g, 4.65 mmol, 92%).
Caution! HF is generated in this reaction, avoid all contact with skin and quench carefully.