2-Methylthiophene → (5-Methylthiophen-2-yl)boronic acid

Participants

Reaction Conditions

Reaction Steps

n-BuLi (2.38M, 16 ml) was slowly added to a solution of 2-methyl thiophene (3.0 g, 31 mmol) in THF (20 ml) at -78° C. The solution was kept at -78° C. for 10 min. then warmed to 0° C. for an additional 0.5 hr. The solution was then transferred by steel canula under nitrogen into a vessel containing triisopropylborate (6.3 g, 33 mmol) in ether (15 ml) at -78° C. The resulting milky white solution was stirred at -78° C. for 20 min. then at room temperature for 2 hours. The reaction was quenched by the addition of 10% aqueous HCl (5.0 ml) and the solution was extracted into ether. The combined ether extracts were extracted with 10M NaOH (2×30 ml), the aqueous extracts were acidified with dilute HCl to pH 2 and extracted into ether (3×25 ml). The combined ether extracts were washed once with water (10 ml), once with brine (10 ml) and dried and evaporated to give 3.91 g 2-methylthiophene-5-boronic acid as a light brown solid. This was used in the next step with no further purification.

Provenance & Evidence