Sodium borohydride → cis-5-Propyl-4,5,6,7-tetrahydro-1-benzothiophen-4-amine

Participants

Reaction Steps

To a solution of sodium borohydride (4.63 g) in ethylene glycol dimethyl ether (150 ml) at 0° C. under N2 was added titanium tetrachloride (6.89 ml). After 5 min, (4Z)-5-propyl-6,7-dihydro-1-benzothiophen-4(5H)-one oxime (6.25 g) in 50 ml of ethylene glycol dimethyl ether was added dropwise to a blue solution. The reaction mixture was stirred at ambient temperate for 24 h and carefully quenched at 0° C. with 2 N NaOH. The aqueous layer was extracted with methylene chloride (3×200 ml), dried MgSO4, filtered and concentrated. MPLC chromatography on a biotage 40 L column with 2–4% methanol/methylene chloride with 0.5% ammonium hydroxide provided Cis-5-propyl-4,5,6,7-tetrahydro-1-benzothiophen-4-amine (2.2 g): 1H NMR (300 MHz, CDCl3) δ) 7.10, 6.96, 3.92, 2.90–2.72, 1.72, 1.47–1.36, 0.98; HRMS (FAB) calcd for C11H17NS+H 196.1160, found 196.1164. and trans-5-propyl-4,5,6,7-tetrahydro-1-benzothiophen-4-amine (2.68 g) as an oil: 1H NMR (300 MHz, CDCl3) δ) 7.10, 7.02, 3.59, 2.78, 2.07, 1.66–1.48, 1.38–1.24, 0.96; HRMS (FAB) calcd for C11H17NS+H 196.1160, found 196.1157.

Provenance & Evidence