[CH2:1]([N:3]1[C:11]2[C:6](=[CH:7][CH:8]=[CH:9][C:10]=2Br)[CH:5]=[CH:4]1)[CH3:2].[Li]C(C)(C)C.CCCCC.C(=O)=O.[C:26](OC)(=[O:31])[C:27]([O:29][CH3:30])=[O:28]>C1COCC1.CCOC(C)=O>[CH3:30][O:29][C:27](=[O:28])[C:26]([C:10]1[CH:9]=[CH:8][CH:7]=[C:6]2[C:11]=1[N:3]([CH2:1][CH3:2])[CH:4]=[CH:5]2)=[O:31]A solution of 1-ethyl-7-bromoindole (2.1 g, 9.4 mmol) in THF (50 mL) was cooled to −78° C. and a 1.7 M solution of tBuLi in pentane (13.8 mL, 23.5 mmol) was added dropwise over 10 min. After 15 min, the resultant brown solution was transferred over 30 min via a cannula cooled with dry ice to a solution of dimethyl oxalate (3.88 g, 32.9 mmol) in THF (40 mL) maintained at −78° C. After 15 min, the mixture was allowed to warm to room temperature and stirred 4 h. The brown solution was treated with pH 7.0 buffer, poured into EtOAc and the EtOAc washed with pH 7.0 buffer, saturated aq NaHCO3, brine, dried (MgSO4) and concentrated to a brown oil. Flash chromatography (20% EtOAc/hexanes) afforded the title compound (1.8 g, 83%) as a yellow oil, which was used without further purification. 1H NMR (400 MHz, DMSO-d6) 7.9 (d, J=8, 1H), 7.55 (m, 2H), 7.2 (dd, J=8, 8 Hz, 1H), 6.66 (d, J=3 Hz, 1H), 4.25 (q, J=7 Hz, 2H), 3.94 (t, J=7 Hz, 3H). MS (electrospray, m/z) 232 (M++1).
Loading…
