Hydrochloric Acid → 4-Bromo-2-thiophenecarboxylic Acid

Participants

Reaction Steps

To a cooled (0° C.) solution of 10.0 g (47.1 mmol based on 90% purity) of 4-bromothiophene-2-carbaldehyde (Aldrich Chemical Company, Milwaukee, Wis.) in 200 mL of t-butanol was added 100 mL of 20 % (w/v) NaH2PO4 followed by 60 mL (0.566 mol) of 2-methyl-2-butene. Sodium chlorite (70.8 mmol based on 80% purity) in 60 mL of water was added with stirring. After stirring the two-phase mixture vigorously for 16 h at room temperature, the pH of the aqueous layer was adjusted to 1-2 with 20% HCl. The layers were separated and the aqueous layer extracted with EtOAc (2×120 mL). The combined organic layers were dried (Na2SO4) and concentrated in vacuo to afford 9.8 g of an off-white solid. Recrystallization from a minimum of MeCN (three crops) gave the title compound as a white solid (9.02 g, 93%). 1H-NMR (300 MHz, CDCl3) δ7.79 (d, 1H, J=1.5 Hz), and 7.55 (d, 1H, J=1.5 Hz).

Provenance & Evidence