Indole → 3-(1,4-Dioxaspiro[4.5]dec-7-en-8-yl)-1H-indole

Participants

Reaction Conditions

Reaction Steps

To a 2-L three-neck round bottom flask equipped with an overhead stirrer, heating mantel, temperature probe and reflux condenser was added indole (100.0 g, 0.836 mol), 1,4-cyclohexanedione monoethylene ketal (175.10 g, 1.09 mol, 1.3 eq) and methanol (221 mL). To this stirred solution was added KOH pellets (31.5 g, 0.48 mol) all at once and the reaction was heated to 70° C. for 4 hrs. The reaction was judged complete by HPLC. The resulting suspension was filtered, washed with MeOH (150 mL), followed by washing the solid with ethanol (2×150 mL). The product was further dried in a vacuum oven at 60° C. for 30 mins to remove residual solvent and obtain the title compound. 1H NMR (400 MHz, CHLOROFORM-d) δ: 7.97-8.16 (m, 1H), 7.90 (d, J=8.1 Hz, 1H), 7.35 (d, J=7.8 Hz, 1H), 7.05-7.23 (m, 3H), 6.05-6.22 (m, 1H), 3.95-4.12 (m, 4H), 2.72 (ddd, J=1.6, 4.6, 8.4 Hz, 2H), 2.45-2.61 (m, 2H), 1.97 (t, J=6.6 Hz, 2H); mp: 190.7-193.1; Elemental anal calc for C16H17NO2: C, 75.27; H, 6.71; N, 5.49. Found: C, 74.93; H, 6.73; N, 5.37; KF: <0.1.

Provenance & Evidence