8-(Phenylmethylidene)-5,6,7,8-tetrahydroquinoline → 6,7-Dihydro-5H-quinoline-8-one

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A solution of (2) in dichloromethane (100 mL) and methanol (500 mL) was cooled to −78° C. and charged with ozone/oxygen (3 psi, 1.5 ampere). The dark brown solution turned yellow after several hours. When (2) was consumed (TLC), ozone/oxygen flow was stopped. The reaction mixture was purged with nitrogen for 10 m. Methyl sulfide (6 mL) was added, and the mixture was stirred for 30 m at 0° C. The solvents were removed under vacuum and the residue was dissolved in 1 N HCl (500 mL) and washed with diethyl ether (4×150 mL). The aqueous layer was basified to pH ˜7 with NaOH (s), and extracted with ethyl acetate (2×200 mL). The pooled ethyl acetate layers were dried over magnesium sulfate. The mixture was filtered and the solvent was removed under vacuum. The residue was purified by chromatography on silica gel with 90% EtOAc 10% hexane to give 6,7-Dihydro-5H-quinolin-8-one (3) as a solid. The aqueous layer was extracted with chloroform/isopropanol (3:1) several times. The pooled chloroform/isopropanol layers were dried over magnesium sulfate. The mixture was filtered and the solvents were removed under vacuum to give (3). The combined weight of (3) was 17.9 g (122 mmol, 89% over 2 steps).

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