Borane → 5-Fluoro-6-phenyl-2,3-dihydro-1H-indole

Participants

Reaction Conditions

Reaction Steps

A mixture of 6-bromo-5-fluoro-1H-indole (0.214 g, 1 mmol), phenylboronic acid (0.171 g, 1.4 mmol), sodium carbonate (1.06 g, 10 mmol), Pd(PPh3)4 (0.116 g, 0.1 mmol), 1,2-dimethoxyethane (5 mL) and water (5 mL) was stirred under nitrogen at 85° C. for 18 h. The mixture was partitioned between water (20 mL) and DCM (2×30 mL) and the combined extracts were dried (Na2SO4) and evaporated in vacuo to give an oil. Chromatography (SiO2; gradient elution with 0-50% Et2O in petrol) gave 5-fluoro-6-phenyl-1H-indole (0.202 g, 95%) as a pale green solid. MS: [M+H]+=212. A solution of borane in THF (1 M, 1.42 mL) was added to 5-fluoro-6-phenyl-1H-indole (0.20 g, 0.95 mmol) under nitrogen with external cooling using an ice-MeOH bath. The resulting mixture was stirred at 0° C. for 0.5 h, then TFA was added dropwise over 0.1 h. The mixture was stirred at 0° C. for 1 h then a solution of sodium hydroxide (0.8 g, 20 mmol) and water (5 mL) was added dropwise over 0.1 h. The resulting mixture was partitioned between water (20 mL) and DCM (2×30 mL) and the combined organic extracts were dried (Na2SO4) and evaporated in vacuo to give an oil. Chromatography (SiO2; gradient elution with 0-100% Et2O in petrol) gave the title compound (0.17 g, 85%) as an oil. MS: [M+H]+=214.

Provenance & Evidence