Tert-Butylamine → N-tert-Butyl-4,5,6,7-tetrahydrobenzo[b]thiophene-2-carboxamide

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Reaction Steps

A mixture of 4,5,6,7-tetrahydrobenzo[b]thiophene-2-carboxylic acid (500 g, 2.75 mol, 1.0 equiv) and thionyl chloride (655 g, 5.5 mol, 2.0 equiv) was heated under reflux for 3 h. Excess thionyl chloride was removed by distillation under reduced pressure. The residue was taken up in dichloromethane (1.0 L) and a solution of tert-butylamine (402 g, 5.5 mol, 2.0 equiv) in dichloromethane (500 mL) was added with stirring while the temperature of the mixture being kept below 10° C. The resulting solution was stirred at 25° C. for 16 h. Most of the solvent was removed under reduced pressure. The residue was chilled in an ice-bath and 2M KOH solution was introduced slowly to adjust the pH to 11 with stirring. The suspension was filtered and the solid collected, washed three times with water, and dried in vacuum to afford 191a as a white solid (580 g, 80%, over two steps). MS: [M+H]+ 238. 1H NMR (500 MHz, CDCl3) δ 7.02 (s, 1H), 5.77 (s, 1H), 2.65 (t, J=6.0 Hz, 1H), 2.47 (t, J=6.0 Hz, 1H), 1.74-1.70 (m, 4H), 1.35 (s, 9H).

Provenance & Evidence