Triisopropyl borate → (6-Ethoxy-5-(trifluoromethyl)pyridin-3-yl)boronic acid

Alternatively, n-butyl lithium (1.6 M solution in hexane, 0.9 mL, 1.43 mmol) was slowly added to a solution of 5-bromo-2-ethoxy-3-trifluoromethyl-pyridine (352 mg, 1.3 mmol) in 2.6 mL anhydrous Et2O at −78° C. under nitrogen. The mixture was kept at −78° C. for 1 hr, and then to this mixture was added triisopropyl borate (489 mg, 2.6 mmol). The mixture was allowed to warm to ambient temperature overnight. The reaction was quenched by water and the pH was adjusted to 5 by carefully addition of 1N aqueous HCl. Two layers were separated and the aqueous layer was extracted with ethyl acetate three times. The extract was washed with brine, dried over sodium sulfate, and concentrated in vacuo to give 2-ethoxy-3-trifluoromethylpyridine-5-boronic acid as a brown oil (240 mg, 67% yield). The product was used for the next step without purification.

1. customThe reaction was quenched by water
2. additionthe pH was adjusted to 5 by carefully addition of 1N aqueous HCl
3. customTwo layers were separated
4. extractionthe aqueous layer was extracted with ethyl acetate three times
5. washThe extract was washed with brine
6. dry with materialdried over sodium sulfate
7. concentrationconcentrated in vacuo

ORD-Eintrag

ord-69c985d4c4834cda9958efe2d5ac9a5a

Quelldatensatz

uspto-grants-2011_09

DOI

10.6084/m9.figshare.5104873.v1

Patentnummer

US08013001B2