Reaction Steps
A solution of 3,4-dihydro-1-(4-methylphenyl)-4,4-dimethyl-7-bromonaphthalene Compound D) 0.45 g, 1.40 mmol) and THF (2.1 ml) was added to magnesium turnings (0.044 g, 1.82 mmol) at room temperature under argon. Two drops of ethylene dibromide were added, and the solution, which slowly became cloudy and yellow, was heated to reflux for 1.5 hours. In a second flask was added zinc chloride (0.210 g, 1.54 mmol), which was melted under high vacuum, cooled to room temperature and dissolved in THF (3 ml). The Grignard reagent was added to the second flask and, after 30 minutes at room temperature, a solution of ethyl 6-bromo-2-naphthalinecarboxylate (Compound N) 0.293 g, (1.05 mmol) and THF (2 ml) were added. In a third flask was prepared a solution of Ni(PPh3)4 and THF as follows: To a solution of NiCl2(Ph3)2 (0.82 g, 1.25 mmol) and PPh3 (0.66 g, 2.5 mmol) in THF (3.5 ml) was added a 1M solution of diisobutylaluminum hydride and hexanes (2.5 ml, 2.5 mmol), and the resulting solution diluted with THF to a total volume of 15 ml and stirred at room temperature for 15 minute. Three 0.60 ml aliquots of the Ni(PPh3)4 solution were added at 15 minutes intervals to the second flask. The resulting suspension was stirred at room temperature for 2 hours. The reaction was quenched by the addition of 5 ml 1N aqueous HCl and stirred for 1 hour before extracting the products with ethyl acetate. The organic layers were combined, washed with brine, dried (MgSO4), filtered and the solvent removed in-vacuo. The residue was crystalized from hexanes to give 130 mg of pure material. The mother liquor was concentrated under reduced pressure and the residue purified by silica gel chromatography (95:5-hexanes:ethyl acetate) to give an additional 170 mg of the title compound (overall yield=300 mg, 64%) as a colorless solid. 1H NMR (CDCl3) δ 8.57 (s, 1H), 8.05 (dd, 1H, J=1.7, 8.0 Hz), 7.84-7.95 (overlapping d's, 3H), 7.66 (dd, 1H, J=1.7, 8.5 Hz), 7.58 (dd, 1H, J=2.0, 8.0 Hz), 7.48 (d, 1H, J=8.0 Hz), 7.43 (d, 1H, J=2.0 Hz), 7.32 (d, 2H, J=8.0 Hz), 7.21 (d, 2H, J=8.0 Hz), 6.04 (t, 1H, J=4.8 Hz), 4.44 (q, 2H, J=7.1 Hz), 2.40 (s, 3H), 2.39 (d, 2H, J=4.8 Hz), 1.45 (t, 3H, J=7.1 Hz), 1.39 (s, 6H).
