7,8-dihydroquinoline-2,6(1h,5h)-dione synthesis

Yield:944902-15-2 90%

Reaction Conditions:

Stage #1: 1',5',7',8'-tetrahydrospiro<1,3-dioxolane-2,6'(2'H)-quinolin>-2'-onewith toluene-4-sulfonic acid in water; for 3 h;Heating / reflux;
Stage #2: with sodium hydrogencarbonate in water;

Steps:

6

1,5,7,8-Tetrahydro-quinoline-2,6-dione: A mixture of 1,5,7,8-Tetrahydro-quinoline-2,6-dione 6-ethylene glycol ketal (2 g, 9.66 mmoL) and p-toluenesulfonic acid monohydrate (184 mg, 0.97 mmoL) in 30 mL water was heated to reflux for 3 h. TLC showed all the starting ketal disappeared. The mixture was cooled down to room temperature, and sodium bicarbonate was added. The mixture was concentrated and silica gel was added. Purification by column chromatography on silica gel with 5% methanol/methylene chloride provided the desired product in 90% yield. ¹H-NMR(300 MHz, CDCl₃): δ 7.25 (d, J=9.1 Hz, 1 H), 6.49 (d, J=9.1 Hz, 1 H), 3.36 (s, 2 H), 3.11 (t, J=7.0 Hz, 2 H), 2.65 (t, J=7.0 Hz, 2 H). ¹³C-NMR(75 MHz, CDCl₃): δ 207.1, 165.0, 142.8, 142.2, 118.1, 111.2, 40.3, 36.9, 26.0. MS (ESI): 164.20 (M+H).

References:

US2008/176308,2008,A1 Location in patent:Page/Page column 12