Sodium Hydroxide → 5-Ethyl-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)thiophene-2-carboxylic acid
Reaction equation
C[O:2][C:3]([C:5]1[S:6][C:7]([CH2:19][CH3:20])=[C:8]([B:10]2[O:14][C:13]([CH3:16])([CH3:15])[C:12]([CH3:18])([CH3:17])[O:11]2)[CH:9]=1)=[O:4].[OH-].[Na+]>CO>[CH2:19]([C:7]1[S:6][C:5]([C:3]([OH:4])=[O:2])=[CH:9][C:8]=1[B:10]1[O:14][C:13]([CH3:16])([CH3:15])[C:12]([CH3:17])([CH3:18])[O:11]1)[CH3:20]Participants
4
Procedure
Methyl-5-ethyl-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)thiophene-2-carboxylate (2.07 g, 5.05 mmol) was dissolved in methanol (17.7 mL) and 2N NaOH (aq) (17.7 mL, 35.3 mmol). The mixture was stirred at room temperature for 48 h. After hydrolysis was complete, the reaction mixture was concentrated to half volume (to take the methanol off) and then extracted once with diethyl ether (removes excess bis(pinacolato)diboron from previous reaction). The aqueous layer was then acidified with 1N HCl (aq) and extracted 3× with ethyl acetate. The ethyl acetate layers were combined, washed with brine 2×, dried with magnesium sulfate, filtered, and concentrated under reduced pressure. The material was left to dry to give the title compound (quantitative yield). 1H NMR (CDCl3, 500 MHz) δ 8.04 (s, 1H), 3.14 (q, J=7.5, 2H), 1.33 (t, J=7.5, 3H), 1.32 (m, 12H).