Acetone → 6-Bromo-2,2,4-trimethyl-1,2-dihydroquinoline

Participants

Reaction Steps

A dry 500 mL r.b. flask equipped with a magnetic stir bar and a reflux condenser was charged with 4-bromoaniline (35.7g, 0.208 mol) and acetone (250 mL, Aldrich reagent grade). To this solution, I2 (2.637 g, 0.05 equiv) was added turning the solution bright red. The mixture was heated to reflux with constant stirring for 4 days (approximately 90 hours). The reaction was monitored by TLC (20% ethyl acetate/methylene chloride; observed starting material and product under short wave UV). As judged by TLC, 50% of the starting material was consumed during the course of the reaction. The reaction mixture was cooled to room temperature and quenched with saturated Na2S2O3 (200 mL). The aqueous mixture was partitioned into 2 phases using ethyl acetate (200 mL). The organic layer was rinsed with saturated Na2S2O3 (3×75-100 mL) and brine (100 mL). The combined aqueous layers were extracted with ethyl acetate (100 mL). The organic layers were combined and dried over anhydrous sodium sulfate. The crude dark material was purified by flash chromatography (800 mL silica, 50% ethyl acetate/methylene chloride) followed by recrystallization of isolated quinoline (hexane) yielding 8.22 g (15%) of Compound 7 (white crystals). Data for Compound 7: 1H NMR (400 MHz, acetone-d6) 7.06 (d, J=2, 1H), 6.99 (dd, J=8, 2, 1H), 6.42 (d, J=8, 1H), 5.36 (s, 1H), 5.28 (br s, 1H) 1.92 (d, J=2, 3H), 1.24 (s, 6H).

Provenance & Evidence