Methylamine → (5-fluoro-3-methylbenzo[b]thiophen-2-yl)-N-methylmethanamine

Participants

Reaction Steps

To 5-fluoro-3-methyl-benzo[b]thiophene-2-carbaldehyde (5.43 g, 28.0 mmol) was added a solution of 2 M methylamine in methanol (94 mL) and the resulting mixture was stirred overnight at room temperature. The mixture was concentrated under reduced pressure and the residue taken up in ethanol (90 mL). The solution was cooled to 0° C. and then NaBH4 (1.06 g, 28.0 mmol) was added in one portion. The mixture was stirred 4 hr, after which time NaBH4 (0.54 g, 14.0 mmol) was added and the mixture was stirred overnight. The mixture was concentrated under reduced pressure and the residue combined with 1 M NaOH (200 mL). The mixture was extracted with diethyl ether (3×150 mL) and the combined organics were washed with brine (100 mL), dried over Na2SO4, filtered and concentrated under reduced pressure to the title compound (5.26 g, 90%) as a pale yellow oil: 1H NMR (300 MHz, CDCl3) δ7.71 (dd, J=9.0, 4.8 Hz, 1H), 7.27 (dd, J=9.3, 2.6 Hz, 1H), 7.09-7.04 (m, 1H), 4.00 (s, 2H), 2.51 (s, 3H), 2.31 (s, 3H).

Provenance & Evidence