2-AMINO-5-FLUOROBENZENEBORONIC ACID synthesis

Yield:1040400-87-0 78%

Reaction Conditions:

with bis-triphenylphosphine-palladium(II) chloride;triethylamine in 1,4-dioxane for 22 h;Reflux;

Steps:

3.1.2. 4-Fluoro-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)aniline (6b)
To a mixture of 2-bromo-4-fluoroaniline (1000.0 mg, 5.26 mmol), anhydrous Et₃N (2.93 m, 21.04 mmol), PdCl₂(PPh₃)₂ (369.2 mg, 0.53 mmol, 10 mol%) in 20 mL anhydrous dioxane, was added 4,4,5,5-tetramethyl-1,3,2-dioxaborolane (2.30 mL, 15.79 mmol) dropwise.The resulting mixture was refluxed for 22 h and then allowed to cool to rt beforebeing quenched by addition of suitable amounts of sat. aq. NH₄Cl. The crude was subsequentlyextracted using CH₂Cl₂ (3 20 mL) and the combined organic phases werewashed with water (1 x 20 mL), brine (1 20 mL), dried (MgSO₄), filtered and concentratedin vacuo. The concentrate was then evaporated onto celite and purification by silicagel column chromatography (pet. ether/EtOAc, 9:1 v/v) and concentration of the relevantfractions [R_f = 0.33 (pet. ether/EtOAc, 9:1 v/v)] gave the target compound 6b as a redsolid (975.7 mg, 78%), mp 49-50 °C (lit. [78] 50-52 °C); IR (ATR): max 3481, 3388, 2978,2931, 1621, 1431, 1137, 854 cm^-1; ¹H NMR (400 MHz, CDCl₃): δ 7.28 (dd, J = 9.1 Hz, 3.1 Hz,1H), 6.92 (ddd, J = 8.6 Hz, 8.3 Hz, 3.1 Hz, 1H), 6.53 (dd, J = 8.8 Hz, 4.3 Hz, 1H), 4.55 (bs,2H), 1.34 (s, 12H); ¹³C NMR (100 MHz, CDCl₃): δ 155.3 (d, J_CF = 235.0 Hz), 149.9, 121.6 (d,J_CF = 20.3 Hz), 119.8 (d, J_CF = 23.0 Hz), 116.1 (d, J_CF = 6.9 Hz), 83.9, 25.0 (one carbon wasobscured or overlapping); ¹⁹F NMR (376 MHz, CDCl₃): δ 129.0. The spectroscopic dataare in accordance with previously reported data [78].

References:

Albrigtsen, Marte;Andersen, Jeanette H.;Avery, Vicky M.;Håheim, Katja S.;Helgeland, Ida T. Urdal;Kennedy, Emily K.;Lauga, Clémence;Lindbäck, Emil;Matringe, Théodora;Sydnes, Magne O.;Tan, Kah Ni [Molecules,2021,vol. 26,# 11,art. no. 3268]

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