[C:1]([BH3-])#[N:2].[Na+].[Br:5][C:6]1[CH:7]=[C:8]([CH:11]=O)[S:9][CH:10]=1.Cl.CN.C(N(CC)CC)C>C(OCC)(=O)C.O>[Br:5][C:6]1[CH:7]=[C:8]([CH2:11][NH:2][CH3:1])[S:9][CH:10]=1
25.2 g (360 mmol) of sodium cyanoborohydride are added to a solution of 35 g (180 mmol) of 4-bromothiophene-2-carbaldehyde, 62 g (640 mmol) of methylamine hydrochloride and 119 ml (846 mmol) of triethylamine. The reaction medium is stirred at room temperature for 3.5 hours. After addition of water and ethyl acetate and washing with aqueous 1M sodium hydroxide solution, the organic phase is extracted. The ethyl acetate phase is dried over magnesium sulfate, filtered and evaporated. The residue obtained is purified by thin-layer chromatography on silica eluted with a 90/10 to 70/30 heptane/ethyl acetate mixture. 19.7 g (52%) of (4-bromothiophen-2-ylmethyl)methylamine are obtained.
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