p-Toluenesulfonic acid → 2,4,5,6-tetrahydro-1H-benzo[f]quinolin-3-one

Reaction equation

[CH2:1]1[C:10]2[C:5](=[CH:6][CH:7]=[CH:8][CH:9]=2)[CH2:4][CH2:3][C:2]1=O.C1(C)C=CC(S(O)(=O)=[O:19])=CC=1.[NH:23]1C[CH2:26][CH2:25][CH2:24]1>C1(C)C=CC=CC=1>[CH2:26]1[C:1]2[C:10]3[CH:9]=[CH:8][CH:7]=[CH:6][C:5]=3[CH2:4][CH2:3][C:2]=2[NH:23][C:24](=[O:19])[CH2:25]1

Participants

Procedure

2-Tetralone (25 g, 171 mmol) was added to a solution of p-toluenesulfonic acid (3.2 g, 16.8 mmol) and pyrrolidine (15 g, 211 mmol) in toluene (250 ml) and the solution was heated under reflux with a Dean-Stark apparatus. When no more water was distilled off, the solvent was removed to afford the enamine as an yellow oil. Acrylamide (46 g, 647 mmol) was added in one portion to the stirred oil, and the resulting mixture was heated at 100° C. for 2 hours. Water (100 ml) was added to the reaction mixture and pH was adjusted to 3-4 with concentrated hydrochloric acid. The solution was extracted with chloroform and the organic layer was washed with brine, dried over magnesium sulfate, and concentrated under reduced pressure. The residue was washed with ethyl acetate, and dried to afford 1,4,5,6-tetrahydro-2H-benzo[f]quinolin-3-one (28 g, 140 mmol, 82%) as white crystals.