Acetic Acid → (1-cyclobutyl-1H-imidazol-4-yl)-carbamic acid phenyl ester

Temperature

-78 °C

A Parr hydrogenation bottle was charged with 1-cyclobutyl-4-nitro-1H-imidazole (Preparation 1, 3 g, 18 mmol) and ethyl acetate (70 mL) followed by 10% Pd on carbon (1.2 g) under a nitrogen atmosphere. The mixture was hydrogenated for 6 h under 50 psi H2 at 23° C. The mixture was then filtered through a pad of celite which was rinsed with dry methylene chloride (140 mL) into a flame-dried flask. The resulting solution was cooled to −78° C. and diisopropylethylamine (2.3 g, 18 mmol) was added followed by the dropwise addition of phenylchloroformate (2.5 g, 16.2 mmol). After 30 min, methanol (9 mL) containing acetic acid (1.8 mmol) was added. The reaction mixture was transferred to a separatory funnel, was diluted with ethyl acetate (200 mL), and was washed with water (2×). The aqueous layers were extracted with ethyl acetate (2×10 mL). The organic layers were combined, were washed with brine (2×), and were then dried (MgSO4), filtered, and concentrated in vacuo. The crude product was adsorbed onto silica gel and was purified by silica gel chromatography (1:1 hexanes-ethyl acetate) to afford 3 g (65% yield) of (1-cyclobutyl-1H-imidazol-4-yl)-carbamic acid phenyl ester; 1H NMR (400 MHz, CDCl3) δ 7.4–7.3 (m, 2H), 7.22–7.18 (m, 3H), 4.5 (m, 1H), 2.46–2.30 (m, 4H), 1.83 (m, 2H); MS (AP/CI): 258.2 (M+H)+.

1. filtrationThe mixture was then filtered through a pad of celite which
2. washwas rinsed with dry methylene chloride (140 mL) into a flame-dried flask
3. waitAfter 30 min
4. additionwas added
5. customThe reaction mixture was transferred to a separatory funnel
6. washwas washed with water (2×)
7. extractionThe aqueous layers were extracted with ethyl acetate (2×10 mL)
8. washwere washed with brine (2×)
9. dry with materialwere then dried (MgSO4)
10. filtrationfiltered
11. concentrationconcentrated in vacuo
12. customwas purified by silica gel chromatography (1:1 hexanes-ethyl acetate)

ORD record

ord-bf88feb4393b4c36bcb3236484326876

Source dataset

uspto-grants-2006_07

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US07078529B2