C([Li])CCC.CCCCCC.Br[C:13]1[CH:14]=[C:15]([C:21]2[CH:26]=[CH:25][N:24]=[CH:23][CH:22]=2)[CH:16]=[CH:17][C:18]=1[O:19][CH3:20].C([O:29][B:30](OCC)[O:31]CC)C.[Cl-].[NH4+]>O1CCCC1>[CH3:20][O:19][C:18]1[CH:17]=[CH:16][C:15]([C:21]2[CH:26]=[CH:25][N:24]=[CH:23][CH:22]=2)=[CH:14][C:13]=1[B:30]([OH:31])[OH:29]
A solution of n-butyllithium in hexane (1.7 mL of 2.5 M, 4.25 mmol) is added to a stirred solution of 4-(3-bromo-4-methoxyphenyl)pyridine (Example 1b; 1.06 g, 4 mmol) and triethylborate (0.62 g, 4.2 mmol) in dry tetrahydrofuran (20 mL) at −85° C. under an argon atmosphere. The mixture is stirred for 15 min at −80° C., then treated with a saturated aqueous solution of ammonium chloride (60 mL) and extracted with ethyl acetate (2×80 mL). The combined extracts are dried (Na2SO4), filtered and the solvent is evaporated off under reduced pressure to yield the crude product which is purified by recrystallisation from ethyl acetate-hexane to give 2-methoxy-5-(pyridin-4-yl)phenylboronic acid as a beige crystalline solid, m.p. 194-200° C. and having the following physical characteristics:
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