Synthesis
A mixture of 4-(8-methoxynaphthalen-2-yl)-2-methyl-1,2,3,4-tetrahydroisoquinoline maleate (57 g, 223 mmol), potassium hydroxide (43 g, 760 mmol), and hydrazine hydrate (26 m1, 830 mmol) in diethylene glycol (2,865 ml) was stirred for 3 hr at 195 C. After cooling to below 40C, the mixture was diluted with water (300 ml), poured into 3 M NaOH and washed three times with dichloromethane. Brine was added to break up the emulsion. The aqueous layer was acidified to pH 1 with 6M HCl and extracted three times with methyl tert-butyl ether. The combined organic extracts were dried with magnesium sulfate to give 4-(4-bromophenyl)butyric acid (41 g, 75%). The product of the previous step (97 g, 397 mmol) was added to polyphosphoric acid (580 g) and the resulting mixture was stirred at 90C for 10 min. After cooling to 0C, 6 M NaOH was added and the mixture was extracted with methyl tert-butyl ether. The organic extract was dried with magnesium sulfate to give 7-bromo-3,4-dihydronaphthalen-1-one (49 g, 55%), chromatographed (6:1 to 4:1 heptane/ethyl acetate) and recrystallized from cyclohexane to give the product 7-bromo-3,4-dihydro-2H-1-naphthalenone.
