Hydrochloric Acid → 3,5-Dimethyl-2-thiophenecarboxylic acid

Participants

Reaction Conditions

Reaction Steps

2.2 equivalents of 2.0 M LDA solution in heptane/THF/ethylbenzene (0.97 mL, 1.019 mol) was added to a solution of 3-methylthiophene-2-carboxylic acid (1.42 g, 10 mmol) in anhydrous THF (20 mL) at 0° C. The reaction mixture was stirred at 0° C. for 1.5 hr; and then methyl iodide (1.4 mL, 22 mmol) was added. The resulting mixture was stirred at 0° C. for an additional 2 hr, acidified with 2N HCl and extracted with methylene chloride (4×50 mL). The organic layers were then combined, concentrated and separated via HPLC to give 3,5-dimethylthiophene-2-carboxylic acid Compound 4A as a white powder. 1H NMR (300 MHz, CD3OD) δ 6.72 (s, 1H), 2.43 (s, 3H), 2.46 (s, 3H); MS (ESI) m/z: 155 (M−H+). Using the procedure of Example 1, Compound 1E was acylated with Compound 4A mediated by DIC/HOBt in anhydrous DMF to produce Compound 33 (73% yield). 1H NMR (300 MHz, (CD3)2SO) δ 9.88 (s, br, 1H), 7.85 (s, br, 2H), 7.78 (q, 4H), 7.18 (s, br, 2H), 6.92 (s, 1H), 2.58 (s, 3H), 2.55 (s, 3H); MS (ESI) m/z: 393 (M+H+), 415 (M+Na+).

Provenance & Evidence