Acetic Acid → 3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-4H,5H,6H-pyrrolo[1,2-b]pyrazole

To a solution of 3-bromo-5,6-dihydro-4H-pyrrolo[1,2-b]pyrazole (73.5 g, 390 mmol) in THF (600 mL) was slowly added n-butyllithium (1.6 M in hexanes, 300 mL, 480 mmol) at −78° C. After 45 minutes, triisopropylborate (111 mL, 480 mmol) was added at −78° C., and the reaction mixture was allowed to warm to ambient temperature. After 1 hour, pinacol (1.8 M in THF, 300 mL, 540 mmol) was added. After 5 minutes, acetic acid (24 mL, 420 mmol) was added. After 30 minutes, the reaction mixture was filtered through CELITE, washed with saturated aqueous sodium bicarbonate solution, and extracted with ethyl acetate (2×500 mL). The organic layers were combined, dried over magnesium sulfate, and concentrated under reduced pressure. The residue was purified by chromatography on silica gel to afford 3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5,6-dihydro-4H-pyrrolo[1,2-b]pyrazole. MS ESI calc'd. for C12H20BN2O2 [M+H]+ 235. found 235. 1H NMR (300 MHz, CDCl3) δ 7.77 (s, 1H), 4.12 (t, J=6.9 Hz, 2H), 2.97 (t, J=6.9 Hz, 2H), 2.60 (t, J=6.9 Hz, 2H), 1.29 (s, 12H).

1. customat −78° C
2. waitAfter 1 hour
3. waitAfter 5 minutes
4. waitAfter 30 minutes
5. filtrationthe reaction mixture was filtered through CELITE
6. washwashed with saturated aqueous sodium bicarbonate solution
7. extractionextracted with ethyl acetate (2×500 mL)
8. dry with materialdried over magnesium sulfate
9. concentrationconcentrated under reduced pressure
10. customThe residue was purified by chromatography on silica gel

ORD record

ord-9f235a087c4644dc927146ae557cf6fa

Source dataset

uspto-grants-2015_12

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US09216173B2