Cesium carbonate → N,N-Dimethyl-2-(5-thiophen-2-yl-1H-indol-3-yl)-acetamide

Participants

Reaction Steps

A solution of 2-(5-bromo-1H-indol-3-yl)-N,N-dimethyl-acetamide (Example 2) (227 mg, 0.81 mmol) in DME (5 mL) is degassed by sparging with argon for 10 minutes. Then thiophene-2-boronic acid (155 mg, 1.21 mmol), caesium carbonate (658 mg, 2.02 mmol), and π-allyl tri-isopropylphosphino palladium bromide (15.7 mg, 0.04 mmol) are added, and the mixture is heated under reflux. Two additional portions of caesium carbonate (103 mg, 0.81 mmol) are added after 20 hours and 24 hours to bring the reaction to completion. The black reaction mixture is poured into 2 N NaOH (10 mL), and extracted twice with ethyl acetate. After removal of the solvent, the residue is chromatographed on silica (CHCl3:MeOH 29:1 v:v) to give the title product (121 mg, 54%). 1H-NMR (CDCl3, 300 MHz) δ 2.96, 2.98 (2 s, 3H each, 2 CH3); 3.77 (s, 2H, CH2); 6.84 (d, 3J=2.2 Hz, H-2); 7.06 (dd, 3J=5.0 Hz, 3J=3.6 Hz, thiophene H-4); 7.21 (d, thiophene H-5); 7.21 (d, 3J=8.4 Hz, H-7); 7.25 (d, thiophene H-3); 7.40 (dd, 4J=1.8 Hz, H-6); 7.70 (d, H-4); 9.16 (br s, NH). 13C-NMR (CDCl3, 75 MHz) δ 31.02 (CH2); 36.00, 38.00 (2 CH3); 109.05 (C-3); 112.17 (C-7); 116.22 (C-4); 121.08 (C-6); 122.25 (thiophene C-3); 123.70 (thiophene C-5); 124.31 (C-2); 126.29 (thiophene C-2); 127.83 (C-9); 128.15 (thiophene C-4); 136.27 (C-8); 146.56 (C-5); 172.16 (CO).

Provenance & Evidence