N-Fluorobenzenesulfonimide → 10-Fluoro-3,4,6,7,8,9-hexahydropyrazino[1,2-a]indol-1(2H)-one

Temperature

-78 °C

Into a 2-L 4-necked round-bottom flask purged and maintained with an inert atmosphere of nitrogen was placed a solution of 119a (40 g, 148.62 mmol, 1.00 equiv) in tetrahydrofuran (200 mL), followed by the addition of n-BuLi (2.4 M) (218 mL, 3.50 equiv) dropwise with stirring at −78° C. The resulting solution was stirred at −40° C. for 3 h. To this was added a solution of N-fluorobenzenesulfonimide (98.7 g, 313.33 mmol, 2.10 equiv) in tetrahydrofuran (200 mL) dropwise with stirring at −78° C. The resulting solution was stirred at room temperature for 3 h, quenched by the addition of 200 mL of water and extracted with 3×500 mL of ethyl acetate. The combined organic layers were dried over anhydrous sodium sulfate and concentrated under vacuum. The crude product (30 g) was purified by Prep-HPLC with the following conditions (mobile phase, A: 0.05% trifluoroacetic acid/water; B: CH3CN; gradient: 10% B-25% B) to afford 5.05 g (16%) of 119b as a white solid. MS: [M+H]+ 209. 1H NMR (300 MHz, CDCl3) δ 6.16 (br, 1H), 3.90-3.86 (m, 2H), 3.65-3.62 (m, 2H), 2.53-2.47 (m, 4H), 1.88-1.80 (m, 2H), 1.77-1.72 (m, 2H).

1. customInto a 2-L 4-necked round-bottom flask purged
2. temperaturemaintained with an inert atmosphere of nitrogen
3. stirringThe resulting solution was stirred at −40° C. for 3 h
4. stirringwith stirring at −78° C
5. stirringThe resulting solution was stirred at room temperature for 3 h
6. customquenched by the addition of 200 mL of water
7. extractionextracted with 3×500 mL of ethyl acetate
8. dry with materialThe combined organic layers were dried over anhydrous sodium sulfate
9. concentrationconcentrated under vacuum
10. customThe crude product (30 g) was purified by Prep-HPLC with the following conditions (mobile phase

ORD record

ord-9ea2816db56547d28c28d801cd91659d

Source dataset

uspto-grants-2015_02

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08946213B2