Lithium Hydroxide → 1-ethyl-4-(3-methoxy-phenylethynyl)-1H-pyrrole-2-carboxylic acid

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To a solution of 1-ethyl-4-(3-methoxy-phenylethynyl)-1H-pyrrole-2-carboxylic acid ethyl ester (3.5 g, 11.76 mmol) in dioxane (70 mL) was added LiOH (2M, 35 mL). The reaction mixture was stirred at room temperature for 3 days, and then concentrated in vacuo. The residue was dissolved in H2O (30 ml) and extracted with ether. Under cooling the aqueous was acidified with HCl (3N) and extracted with EtOAc. The organic extracts were dried over MgSO4. Evaporation and recrystallzation from ether and hexane gave the 1-ethyl-4-(3-methoxy-phenylethynyl)-1H-pyrrole-2-carboxylic acid intermediate as light yellow solid (2.55 g, 79% yield), mp 129° C., 1H NMR (400 MHZ, CDCl3) δ 1.26 (t, 3H), 3.73 (s, 3H), 4.26-4.28 (q, 2H), 6.96-6.97 (m, 2H), 6.99-7.0 (m, 2H), 7.23-7.24 (m, 1H), 7.46 (s, 1H), 12.46 (bs, 1H), MS m/e (M−H)− 268.1.

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