Hydrazine hydrate (1:1) → 1,5-Dihydro-3-phenethyl-[1,2]diazepino[4,5,6-cd]-indol-6-one

Participants

Reaction Steps

A solution of methyl indole-4-carboxylate (250 mg, 1.43 mmol) in dichloroethane (3 mL) was treated with 3-phenylpropionyl chloride (361 mg, 2.14 mmol) at room temperature. The orange solution was cooled to 0° C. and treated with aluminum chloride (572 mg, 4.29 mmol). The reaction mixture was stirred at room temperature for 2 h, then poured into ice-cold 1M aqueous HCl. The aqueous solution was adjusted to pH=8 with 1M NaOH, and extracted with CH2Cl2 (10 mL×3). The organic solution was washed with water and brine, dried (Na2SO4), filtered, and concentrated to give methyl 3-(3-phenylpropionyl)-indole-4-carboxylate as a pale-yellow solid, 395 mg (90%). A solution of the 3-(3-phenylpropionyl)-4-carboxy indole (95.5 mg, 0.31 mmol) in MeOH (3 mL) and HCl (0.1 mL) was treated with hydrazine hydrate (47 mg, 0.93 mmol) and the solution was heated at reflux for 8 h. The solution was cooled in an ice/water bath and the precipitated solid was collected by filtration to give 1,5-dihydro-3-phenethyl-[1,2]diazepino[4,5,6-cd]-indol-6-one, 60.2 mg (71%). The crude product was purified by radial chromatography (2 mm SiO2, 5:1 hexanes: EtOAc) to give a yellow solid. mp 182-183.5° C.; 1H NMR (300 MHz, d6-DMSO) δ2.80 (m, 2H), 2.84 (m, 2H), 7.22 (m, 2H), 7.31 (m, 4H), 7.54 (m, 2H), 7.81 (s, 1H), 10.19 (s, 1H), 11.92 (br s, 1H); Anal. (C10H7N3O.0.1 H2O) C, H N.

Provenance & Evidence