[CH:1]1([C:4]2[CH:12]=[C:11]3[C:7]([CH:8]=[CH:9][N:10]3[C:13]([O:15][C:16]([CH3:19])([CH3:18])[CH3:17])=[O:14])=[CH:6][CH:5]=2)[CH2:3][CH2:2]1.C([O:23][B:24](OC(C)C)[O:25]C(C)C)(C)C.[Li+].CC([N-]C(C)C)C>C1COCC1>[C:16]([O:15][C:13]([N:10]1[C:11]2[C:7](=[CH:6][CH:5]=[C:4]([CH:1]3[CH2:2][CH2:3]3)[CH:12]=2)[CH:8]=[C:9]1[B:24]([OH:25])[OH:23])=[O:14])([CH3:19])([CH3:18])[CH3:17]To a solution of tert-butyl 6-cyclopropyl-1H-indole-1-carboxylate (1.93 g, 7.51 mmol) and triisopropylborate (2.58 mL, 11.26 mmol) in THF was added LDA (1.5 M in cyclohexane, 7.0 mL, 10.5 mmol) at −78° C. The mixture was stirred at −78° C. for 30 min, quenched with ice water (60 mL) and stirred for 15 min without cooling. The mixture was extracted with ethyl acetate 1:1 in hexane (20 mL). The aqueous layer was acidified with aq. 2 N HCl to pH 5 and then extracted with CH2Cl2 (60 mL). The organic layer was dried over Na2SO4 and concentrated to give 1-(tert-butoxycarbonyl)-6-cyclopropyl-1H-indol-2-ylboronic acid as a solid (2.0 g, 88% yield) that was used in the next step without further purification.
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