[CH2:1]([CH:4]1[CH2:13][C:12]2[C:7](=[CH:8][CH:9]=[CH:10][CH:11]=2)[CH2:6][C:5]1=[O:14])[CH:2]=[CH2:3].C(OC)(OC)OC.[CH:22](O)([OH:24])[CH3:23]>ClCCl.O.C1(C)C=CC(S(O)(=O)=O)=CC=1>[CH2:22]1[O:24][C:5]2([CH:4]([CH2:1][CH:2]=[CH2:3])[CH2:13][C:12]3[C:7](=[CH:8][CH:9]=[CH:10][CH:11]=3)[CH2:6]2)[O:14][CH2:23]1A mixture of 3-(2-propenyl)-2-tetralone (25.9 g, 139 mmol), trimethyl orthoformate (61.3 ml, 554 mmol), ethanediol (57.5 ml, 1.03 mol), p-toluenesulfonic acid monohydrate (0.27 mg, 1.4 mmol) in dichloromethane (650 ml) was stirred at room temperature, under argon for 2 h. Resulting mixture was partitioned between saturated aqueous sodium bicarbonate (1000 ml) and dichloromethane (3×500 ml). The combined organic extracts were washed with brine (500 ml), dried (Na2SO4) and evaporated in vacuo to give a brown oil (34.9 g). Chromatography on silica using 0-10% ether-hexane gradient elution gave the title compound as a yellow oil (20.1 g, 63%).
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