[Br:1][CH2:2][CH2:3][CH2:4][CH2:5][CH2:6][CH2:7][CH2:8][CH2:9][CH2:10][CH2:11][CH2:12][OH:13].[O:14]1[CH:19]=[CH:18][CH2:17][CH2:16][CH2:15]1.C1(C)C=CC(S(O)(=O)=O)=CC=1.C([O-])(O)=O.[Na+]>ClCCl.C(OCC)(=O)C>[Br:1][CH2:2][CH2:3][CH2:4][CH2:5][CH2:6][CH2:7][CH2:8][CH2:9][CH2:10][CH2:11][CH2:12][O:13][CH:15]1[CH2:16][CH2:17][CH2:18][CH2:19][O:14]1
50 g (0.199 mol) of 11-bromo-1-undecanol (Aldrich) was dissolved in 500 ml of dichloromethane, and the mixture was cooled to 0° C. 22.15 ml (0.242 mol) of dihydropyran were added dropwise over a period of two hours; the reaction was started by addition of a few crystals of p-toluenesulphonic acid at the beginning of the addition. After the addition was complete, the reaction mixture was stirred for 15 min and stopped by addition of 0.5 g of NaHCO3. After evaporation of the dichloromethane, the pale yellow syrup obtained was dissolved in ethyl acetate and purified by filtration through silica gel. Yield=65.3 g (98%).
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