ChemicalBook CAS DataBase List 2-Furanboronic acid

2-Furanboronic acid synthesis

11synthesis methods

Product Name:2-Furanboronic acid
CAS Number:13331-23-2
Molecular formula:C4H5BO3
Molecular Weight:111.89

2-(Furan-2-yl)-6-methyl-1,3,6,2-dioxazaborocane-4,8-dione, 2-Furanboronic acid MIDA ester

1104637-62-8

13331-23-2

The general procedure for the synthesis of 2-furanboronic acid from 2-(furan-2-yl)-6-methyl-1,3,6,2-dioxaborolane-4,8-dione was as follows: a solution of MIDA borate (5 mmol) in THF (50 mL) was added to a 100 mL flask fitted with a stir bar under an ambient atmosphere followed by the addition of an aqueous 1.0 M NaOH solution (15 mL ). The reaction mixture was stirred vigorously for 20 minutes. Upon completion, the mixture was transferred to a partition funnel and diluted with ether (50 mL) and 0.5 M pH 7 sodium phosphate buffer (50 mL). The phases were separated after sufficient shaking. The aqueous phase was extracted with a solvent mixture of THF/ether (1:1, 2 x 25 mL). The organic phases were combined, dried with anhydrous MgSO4, filtered and concentrated in vacuum. The residual solvent was co-evaporated with acetonitrile and the resulting solid was dried under vacuum at about 1 Torr for 30 min. The resulting boric acid was analyzed by 1H-NMR to be >95% pure and was immediately used in the subsequent cross coupling reaction. Specific examples are as follows: 2-furanboronic acid (0.531 g, 95% yield) was obtained as an off-white solid using MIDA borate (1.127 g, 5.002 mmol) following the general procedure described above.TLC (unfolding reagent: ethyl acetate) Rf = 0.46, stained with potassium permanganate to develop color.1H-NMR (500 MHz, DMSO-d6:D2O 1H-NMR (500 MHz, DMSO-d6:D2O 95:5, with TMS) δ 7.81 (dd, J = 1.5, 5.5 Hz, 1H), 7.07 (dd, J = 3.0, 0.5 Hz, 1H), 6.48 (dd, J = 3.5, 2.0 Hz, 1H). 13C-NMR (125 MHz, DMSO-d6:D2O 95:5, with TMS) δ 146.4, 121.5, 110.3. 121.5, 110.3. HRMS (EI+) calculated value C4H3O3B [M]+: 112.0332, measured value: 112.0332.

1104637-62-8
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13331-23-2
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Yield:13331-23-2 95%

Reaction Conditions:

Stage #1:2-(furan-2-yl)-6-methyl-1,3,6,2-dioxazaborocane-4,8-dione with water;sodium hydroxide in tetrahydrofuran at 23; for 0.333333 h;
Stage #2: in tetrahydrofuran;diethyl ether; pH=7Aqueous phosphate buffer;

Steps:

5
The general method for synthesizing unprotected organoboronic acids was as follows. Under ambient atmosphere, to a 100 mL flask equipped with a stir bar and charged with MIDA boronate (2) (5 mmol) as a solution in THF (50 mL) was added aqueous NaOH (1.0 M, 15 mL). The mixture was vigorously stirred for 20 min. The mixture was then transferred to a separatory funnel and was diluted with EbO (50 mL) and 0.5 M pH 7 sodium phosphate buffer (50 mL). The mixture was shaken, and the phases were separated. The aqueous phase was extracted with THFiEt₂O (1 :1 , 2 x 25 mL). The combined organics were dried over MgSO₄, filtered and concentrated in vacuo. Residual solvent was co-evaporated with MeCN, and the resulting solid was placed under vacuum ( ~ 1 Torr) for 30 min. All boronic acids thus obtained were judged to be > 95% pure by ¹ H-NMR and were utilized in cross-coupling reactions immediately after preparation. An example of this method is depicted in the scheme below. To form unprotected organoboronic acid 1a, the general procedure was followed using MIDA boronate 2a (1.127 g, 5.002 mmol) to yield the 1a as an off white solid (0.531 g, 95%). TLC (EtOAc) Rf = 0.46, stained with KMnO₄. ¹H-NMR (500 MHz, DMSO-d₆:D₂O 95:5 w/ TMS) δ 7.81 (dd, / = 1 .5, 0.5 Hz, 1 H), 7.07 (dd, / = 3.0, 0.5 Hz, 1 H), 6.48 (dd, / = 3.5, 2.0 Hz, 1 H). ¹³C-NMR (125 MHz, DMSO-d₆:D₂O 95:5 w/ TMS) δ 146.4, 121.5, 1 10.3. HRMS (El +) Calculated for C₄HsO₃B (M) ⁺ : 1 12.0332, Found: 1 12.0332.

References:

THE BOARD OF TRUSTEES OF THE UNIVERSITY OF ILLINOIS;BURKE, Martin, D.;KNAPP, David, M.;GILLIS, Eric, P. WO2010/36921, 2010, A2 Location in patent:Page/Page column 41

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