Hydrochloric Acid → 1-benzyl-6-methoxy-3,4-dihydro-1H-naphthalen-2-one

Participants

Reaction Steps

A solution of 51 g (0.289 mol) of 6-methoxy-2-tetralone of formula A-1 wherein Rx is methoxy, and 24.2 mL (0.289 mol) of pyrrolidine in 1.5 L of toluene was heated to reflux, over a Dean-Stark trap, overnight. After removal of the azeotroped water, the reaction mixture was cooled to RT, concentrated to an oil, and dissolved in 725 mL of dioxane. To this solution was added 52 mL (0.434 mol) of benzyl bromide and the resulting solution was heated to reflux overnight. Water (100 mL) was added to the solution, and the resultant mixture was heated to reflux for an additional 2 h. The mixture was cooled to room temperature and poured into a solution of 1 N HCl and extracted 3 times with EtOAc. The organic layers were washed with H2O and saturated NaHCO3, then dried over Na2SO4, filtered, and evaporated to dryness. The crude product was purified by flash chromatography over SiO2 using 10% EtOAc to 15% EtOAc in hexanes as the gradient eluant to give 65.2 g of the title product of this preparation as a yellow oil (85%). IR (neat) 2937, 1712, 1500 cm−1; 1H NMR (400 MHz, CDCl3) δ 2.41-2.59 (m, 3H), 2.76 (dt, 1H, J=5.4, 15.5), 3.15-3.70 (m, 2H), 3.67 (t, 1H, J=6.3), 3.77 (s, 3H), 6.67-6.70 (m, 2H), 6.81 (d, 1H, J=8.1), 6.87-6.89 (m, 2H), 7.13-7.17 (m, 3H); 13C NMR (100 MHz, CDCl3) δ 27.44, 38.19, 39.19, 54.13, 55.14, 112.11, 112.96, 126.30, 128.07, 128.26, 129.35, 129.53, 138.05, 138.20, 158.30, 212.41; MS m/z 267 (M+H)+.

Provenance & Evidence