Sodium Carbonate → HCID 22350424, compound

Participants

Reaction Steps

In a flask are placed 2-bromothiophene-5-carboxylic acid (1.20 g, 5.81 mmol), 5-methylthiophene-2-boronic acid (0.99 g, 6.97 mmol), and Pd(PPh3)4 (0.20 g, 0.17 mmol). The flask is then vacuum purged and nitrogen filled (3×). THF (12 mL) is then added by syringe followed by vacuum purge and nitrogen fill (3×). A solution of Na2CO3 (2M, 5.8 mL, 11.6 mmol) is added followed by vacuum purge and nitrogen fill (3×). The reaction mixture is heated to reflux for 19 h then cooled to rt and diluted with water. The aqueous solution is extracted with ether (3×). The aqueous layer is then acidified and extracted with EtOAc (3×). The combined organic layers are dried over MgSO4, filtered, and concentrated to provide an inseparable 3:1 mixture of 2-bromothiophene-5-carboxylic acid and bithiophene product. To separate the compounds the methyl esters are formed: In a flask are placed the aforementioned mixture, MeOH (50 mL) and conc H2SO4 (5 drops) and heated to reflux for 24 h. The solution is concentrated and chromatographed over silica gel (2% acetone-heptane) to provide methyl 5′-methyl-2,2′-bithiophene-5-carboxylate as a solid (0.37 g, 26% 2 steps). 1H NMR (400 MHz, CDCl3) δ 7.69, 7.10, 7.07, 6.73, 3.91, 2.52.

Provenance & Evidence