Pyridiniumtribromide → Methyl-2-bromo-7-chloro-3-cyclohexyl-1H-indole-6-carboxylate

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Reaction Steps

To a mixture of the methyl 7-chloro-3-cyclohexyl-1H-indole-6-carboxylate (1 g, 3.43 mmol) in a mixture of THF/CH2Cl2 (9 ml/9 ml) at r.t. under N2 was added pyridinium tribromide (1.33 g, 4.16 mmol, recrystallized from AcOH), and the reaction mixture stirred at r.t. for 2 hr. The mixture was then diluted with CH2Cl2 (40 ml), and the organics washed with NaHCO3 (30 ml, sat. aq.), followed by hydrochloric acid (30 ml, 1N) and brine (30 ml). After concentration of the organic layer, the residue was purified by Biotage flash chromatography (gradient elution, 0 to 20% EtOAc/Hexane) to gave methyl 2-bromo-7-chloro-3-cyclohexyl-1H-indole-6-carboxylate (841.8 mg, 66%) and to recover the starting material (201 mg). 1H NMR (500 MHz): (CD3OD) δ 7.67 (b d, J=8.5, 1H), 7.59 (d, J=8.5, 1H), 3.93 (s, 3H), 2.89 (m, 1H), 2.00-1.90 (overlapping m, 4H), 1.83-1.78 (overlapping m, 3H), 1.50-1.40 (m, 3H); Analytical HPLC method: Solvent A=10% MeOH-90% H2O-0.1% TFA, Solvent B=90% MeOH-10% H2O-0.1% TFA, Start % B=0, Final % B=100, Gradient time=2 min, Flow Rate=5 ml/min, Column: Xterra MS C18 S7 3.0×50 mm; LC/MS: (ES+) m/z (M+H)+=370.02, 372.03, 374.02, HPLC Rt=2.002 min.

Provenance & Evidence