Ethylene Glycol → 2-Methyl-2-(4-methylphenyl)-1,3-dioxolane

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[CH3:1][C:2]1[CH:7]=[CH:6][C:5]([C:8]([CH3:10])=[O:9])=[CH:4][CH:3]=1.C1(C)C=CC(S(O)(=O)=O)=CC=1.[CH2:22](O)[CH2:23][OH:24]>C1(C)C=CC=CC=1>[CH3:10][C:8]1([C:5]2[CH:6]=[CH:7][C:2]([CH3:1])=[CH:3][CH:4]=2)[O:24][CH2:23][CH2:22][O:9]1

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실험 절차

A mixture of 4-methylacetophenone (1.00 g, 7.45 mmol), p-toluenesulfonic acid (133 mg, 0.745 mmol) and ethylene glycol (1.20 mL, 22.4 mmol) in dry toluene (20 mL) was heated at reflux with a Dean-Stark apparatus under nitrogen for 24 h. The mixture was allowed to cool to room temperature and the solvent was evaporated in vacuo. The residue was taken up in ether (20 mL) and the solution was washed with saturated sodium bicarbonate solution (2×10 mL) and brine (1×10 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-dioxolane (23) as a colourless oil (1.05 g, 59%). 1H nmr (200 MHz, CDCl3) 1.65 (s, 3H, CH3), 2.35 (s, 3H, ArCH3), 3.74-3.86 (m, 2H, OCH2), 3.94-4.06 (m, 2H, OCH2), 7.15 (d, J=8.2 Hz, 2H, 2×ArH), 7.37 (d, J=8.2 Hz, 2H, 2×ArH).