Triethyl borate → (6-Ethylpyridin-3-yl)boronic acid

Participants

Reaction Conditions

Reaction Steps

Into a 500-mL 3-necked round-bottom flask (1 atm) purged and maintained with an inert atmosphere of nitrogen, was placed 5-bromo-2-ethylpyridine (3 g, 16.12 mmol, 1.00 equiv) and tetrahydrofuran (200 mL). To the resulting mixture was then added n-BuLi (8.4 mL, 2.5 M) dropwise with stirring at −78° C. The resulting solution was stirred for 30 min at −78° C. in an ethanol/N2 bath. To the resulting mixture was then added triethyl borate (4.7 g, 32.19 mmol, 2.00 equiv) dropwise with stirring at −78° C. The resulting solution was allowed to react, with stirring, overnight at room temperature. The reaction was then quenched by the addition of methanol (20 mL) and water (0.5 mL). The resulting mixture was then concentrated under vacuum. The resulting solution was diluted with methanol (10 mL). The resulting residue (10 mL) was purified by Flash-Prep-HPLC (reversed column) with the following conditions (IntelFlash-1): Column, C18 silica gel; mobile phase, A:water with trifluoroacetic acid (0.05%); B: MeCN=1/100 increasing to A:water with trifluoroacetic acid (0.05%); B: MeCN=20/100 within 25 min; Detector, UV 254 nm to yield of (6-ethylpyridin-3-yl)boronic acid as a white solid.

Provenance & Evidence