Carbon Dioxide → Indole-2-carboxaldehyde

Participants

Reaction Conditions

Reaction Steps

Indole (74) (1.00 g, 8.54 mmol) was dissolved in 50 mL of dry THF. The resulting solution was cooled at −78° C. A solution of 2.5 M of n-butyllithium (3.80 mL, 9.39 mmol) was slowly added to the THF solution and was stirred for 30 min. Carbon dioxide was passed through the reaction mixture over 10 min. The resulting solution was allowed to warm to room temperature. The excess of carbon dioxide was removed under reduced pressure while the solution was concentrated to 25 mL. 50 mL of dry THF was added to the concentrated solution, which was cooled again to −78° C. A solution of 1.7 M of tert-butyllithium (5.00 mL, 8.54 mmol) was slowly added to the THF solution, which was stirred at −78° C. for 1 hour. Anhydrous N,N-dimethylformamide (0.83 mL, 8.5 mmol) was added to the solution. The resulting mixture was warmed to room temperature over a period of 1.5 hours. Water (10 mL) was added and the mixture was stirred for 15 min. Diethyl ether was added. The organic layer was washed with brine (3×). The organic layer was dried over magnesium sulfate, filtered and concentrated in vacuo. The solid was purified over silica gel using 80/20 hexanes/ethyl acetate as eluent to give Compound 75, (0.7129 g, 58%). 1H NMR (500 MHz, CDCl3): d (ppm), 9.88 (s, 1H); 7.77 (d, 1H, J=8.1 Hz); 7.48 (d, 1H, J=8.3 Hz); 7.41 (t, 1H, J=7.0 Hz); 7.3 (s, 1H); 7.20 (t, 1H, J=7.4 Hz). 13C NMR (500 MHz, CDCl3): δ (ppm), 182.89; 138.80; 136.87; 128.25; 124.37; 122.20; 115.60; 113.28.

Provenance & Evidence