2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indol-1-one

Preparation

Tryptamine 380 (9.0 g, 56.2 mmol) and triethylamine (13.8 g, 136.3 mmol) were dissolved in warm toluene (800 mL). Under vigorous stirring, a solution of triphosgene (6.7 g, 22.6 mmol) in toluene (35 mL) was added dropwise and the mixture was stirred for a further 20 min at room temperature. Then, HBr (30% in acetic acid; 13 mL) was added and the mixture was refluxed for 30 min. After cooling to room temperature, water (300 mL) and ethyl acetate (300 mL) were added and, after separation of the layers, the aqueous phase was extracted once more with ethyl acetate (300 mL). The combined organic layers were dried over magnesium sulfate and concentrated in vacuo. The residue was recrystallized from methanol/ethyl acetate (1:1) to afford 7.74 g (74%) of 2,3,4,9-tetrahydro-1H-pyrido[ 3,4-b]indol-1-one 382 as a white solid; mp 184°C.