Methanol → 1,3-Dioxane, 2-(4-chlorophenyl)-2-methyl-

To a stirred mixture of 4-chloroacetophenone (1.3 mL, 10 mmol), triethylformate (2.0 mL, 12 mmol), 1,3-propanediol (2.2 mL, 30 mmol) and dry methanol (1.2 mL) in dry CH2Cl2 (50 mL) was added NBS (53 mg, 0.30 mmol). The mixture was protected from light and stirred at room temperature under an inert atmosphere of nitrogen for 70 h. After the mixture was washed with saturated aqueous sodium bicarbonate solution (20 mL), the aqueous phase was extracted with dichloromethane (3×30 mL). The combined organic solution was washed with water (2×20 mL), brine (1×20 mL), then dried (Na2SO4) and concentrated under reduced pressure. Flash column chromatography of the residue, eluting with 37% aqueous ammonia:ether:hexane (0.02:1:6) afforded 2-(4-chlorophenyl)-2-methyl-1,3-dioxane (20) as a colourless oil (1.1 g, 52%). 1H nmr (200 MHz, CDCl3) 1.49 (s, 3H, CH3), 1.98-2.25 (m, 2H, OCH2CH2CH2O), 3.65-4.10 (m, 4H, OCH2CH2CH2O), 7.30-7.50 (m, 4H, 4×ArH).