1,4-Dibromobutane → Tert-Butyl 1-(4-bromobutyl)cyclopropanecarboxylate

Under a N2 atmosphere at −60° C., a solution of t-butyl cyclopropanecarboxylate (80.05 g, 0.507 mol) and 1,4-dibromobutane (2193 g, 1.01 mol) in dry THF (800 mL) was added dropwise to a solution of LDA (2 M in THF/heptane/ethylbenzene, 380 mL, 0.76 mol) in 1.5 h. Stirring was continued for 5 h, during which the reaction mixture was allowed to slowly reach rt. After that, the reaction mixture was poured into saturated aqueous NH4Cl (1 L). The organic layer was separated and concentrated in vacuo to a smaller volume. The aqueous layer was extracted with Et2O (3×200 mL). The combined organic layers were washed with saturated aqueous NH4Cl (2×400 mL) and brine (400 mL) and dried. The remaining residue was purified by fractional distillation under reduced pressure to give 103b (51.4 g, 94% pure by GC, 34%) as a slightly yellow oil. bp: T=93-96° C. (p=0.075-0.087 Torr). 1H NMR: δ 3.40 (t, J=6.8 Hz, 2H), 1.85 (quintet, J=7.1 Hz, 2H), 1.65-1.46 (m, 4H), 1.43 (s, 9H), 1.12 (q, J=3.5 Hz, 2H), 0.60 (q, J=3.5 Hz, 2H). 13C NMR: δ 174.0, 79.8, 33.6, 33.2, 32.8, 27.9 (3×), 26.3, 23.9, 15.1 (2×). HRMS calcd for C12H21BrO2 (MH+): 277.0803, found: 277.0807.

1. customwas allowed to slowly reach rt
2. customThe organic layer was separated
3. concentrationconcentrated in vacuo to a smaller volume
4. extractionThe aqueous layer was extracted with Et2O (3×200 mL)
5. washThe combined organic layers were washed with saturated aqueous NH4Cl (2×400 mL) and brine (400 mL)
6. customdried
7. distillationThe remaining residue was purified by fractional distillation under reduced pressure

ORD-Eintrag

ord-df440e32e66449b4b7b6d15ee2947d93

Quelldatensatz

uspto-grants-2014_02

DOI

10.6084/m9.figshare.5104873.v1

Patentnummer

US08642653B2