反应详情

To a stirred mixture of 4-methylacetophenone (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 dichloromethane (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 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-methyl-2-(4-methylphenyl)-1,3-dioxane (22) as a colourless oil (480 mg, 24%). 1H nmr (200 MHz, CDCl3) 1.50 (s, 3H, CH3), 1.96-2.25 (m, 2H, OCH2CH2CH2O), 2.37 (s, 3H, ArCH3), 3.70-4.00 (m, 4H, OCH2CH2CH2O), 7.23 (d, J=8.3 Hz, 2H, 2×ArH), 7.33 (d, J=8.3 Hz, 2H, 2×ArH).

1. washAfter the mixture was washed with saturated sodium bicarbonate solution (20 mL)
2. extractionthe aqueous phase was extracted with dichloromethane (3×30 mL)
3. washThe combined organic solution was washed with water (2×20 mL), brine (1×20 mL)
4. dry with materialdried (Na2SO4)
5. concentrationconcentrated under reduced pressure
6. washFlash column chromatography of the residue, eluting with 37% aqueous ammonia:ether:hexane (0.02:1:6)