Aniline → Dimethyl indole-2,3-dicarboxylate

Participants

Reaction Conditions

Reaction Steps

A 300 mL RBF was charged with N,N-Dimethylacetamide (DMA) (144 ml) and Acetic Acid (48.1 ml) was degassed with O2 for 5 min. To this was added aniline (2.94 ml, 32.2 mmol), dimethyl but-2-ynedioate (3.96 ml, 32.2 mmol), and Pd(OAc)2 (0.723 g, 3.22 mmol) and the reaction was heated to 115° C. under an atmosphere of O2. After 18 h, the reaction was cooled to ambient temperature, filtered through a pad of celite, diluted with EtOAc and washed with H2O. The organic was washed with brine, dried (MgSO4), filtered and concentrated. The residue was purified by ISCO (0-50% EtOAc-hexanes: 120 g SiO2) to afford dimethyl 1H-indole-2,3-dicarboxylate (3 g, 12.86 mmol, 39.9% yield) as a yellow solid. The indole was dissolved in DMF (50 mL), treated with Cs2CO3 (6.30 g, 19.33 mmol), 4-Fluorobenzyl chloride (1.929 ml, 16.11 mmol) and KI (5.35 g, 32.2 mmol) and heated to 90° C. After 2 h, the reaction mixture was cooled to ambient temperature and partitioned between EtOAc and sat. aq. NH4Cl. The organic layer was washed with water (5×), brine, dried (MgSO4), filtered and concentrated in vacuo. The residue was purified on ISCO (0-100% EtOAc-hexanes) to afford dimethyl 1-(4-fluorobenzyl)-1H-indole-2,3-dicarboxylate (3.79 g, 11.10 mmol, 34.5% yield) as a yellow solid. LCMS (m/z) ES+=342 (M+1).

Provenance & Evidence