[CH3:1][C:2]1([CH3:20])[C:6]([CH3:8])([CH3:7])[O:5][B:4]([C:9]2[CH:10]=[N:11][N:12]([CH:14]3[CH2:19][CH2:18][NH:17][CH2:16][CH2:15]3)[CH:13]=2)[O:3]1.[CH2:21]=O.[BH4-].[Na+]>CO>[CH3:21][N:17]1[CH2:18][CH2:19][CH:14]([N:12]2[CH:13]=[C:9]([B:4]3[O:5][C:6]([CH3:7])([CH3:8])[C:2]([CH3:20])([CH3:1])[O:3]3)[CH:10]=[N:11]2)[CH2:15][CH2:16]1A mixture of 4-[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazol-1-yl]piperidine (0.500 g, 1.80 mmol) and 37% aqueous formaldehyde solution (0.269 mL, 3.61 mmol) in MeOH (10.0 mL) were combined and stirred at 40° C. for 2 h. Then sodium borohydride (205 mg, 5.41 mmol) was carefully added to the reaction mixture left to stir for 16 h. The reaction was concentrated in vacuo to a solid. The crude product was dissolved in EtOAc and washed with water several times. The organic layer was collected, dried with sodium sulfate, filtered and concentrated in vacuo to a solid to yield the desired product. 1H NMR (400 MHz, CD3OD): δ 7.90 (s, 1H), 7.67 (s, 1H), 4.16-4.26 (m, 1H), 3.00 (d, J=12.13 Hz, 2H), 2.34 (s, 3H), 2.25 (td, J=11.75, 3.28 Hz, 2H), 2.03-2.15 (m, 4H), 1.31 (s, 12H).
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