C(=O)(O)[O-].[Na+].Br[CH:7]([CH2:21][CH2:22][CH2:23][CH3:24])[C:8]([C:10]1[CH:11]=[C:12]([NH:17]C(=O)C)[CH:13]=[CH:14][C:15]=1[OH:16])=O.[BH4-].[Na+].[ClH:27]>CO>[ClH:27].[CH2:21]([C:7]1[O:16][C:15]2[CH:14]=[CH:13][C:12]([NH2:17])=[CH:11][C:10]=2[CH:8]=1)[CH2:22][CH2:23][CH3:24]
Sodium bicarbonate (3.36 g, 40.0 mmol) was added in several portions to a stirred boiling mixture of N-[3-(2-bromohexanoyl)-4-hydroxyphenyl]acetamide [6a] (13.13 g, 40.0 mmol) and methanol (30 mL). The mixture was stirred under reflux conditions for 2 hour. Sodium borohydride (1.51 g, 40.0 mmol) was added in several portions to the mixture at 0-5° C. (ice/water bath). The mixture was stirred for 30 min at the same temperature and 15% hydrochloric acid (100 mL) was added. The solution was stirred for 4 hours under reflux conditions and for 1 hour at 0-5° C. (ice/water bath). The precipitated crystals were filtered off, washed on the filter with water (20 mL) and ethyl acetate (20 mL) and dried to give 7.62 g (84.5% yield from 3 steps) of 2-butyl-5-benzofuranamine hydrochloride [12a] as off-white crystals with mp 190-193° C. (dec.).
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