Br[C:2]1=[CH:3][CH2:4][CH2:5][CH2:6][CH2:7][CH2:8][CH:9]1[O:10][CH2:11][CH2:12][CH:13]=[CH2:14].C1CCN2C(=NCCC2)CC1.CCOC(C)=O.Cl>CS(C)=O>[CH2:11]([O:10][CH:9]1[CH2:8][CH2:7][CH2:6][CH2:5][CH2:4][C:3]#[C:2]1)[CH2:12][CH:13]=[CH2:14]The compound 2 (2.04 g, 7.8 mmol) is dissolved in anhydrous DMSO (10 ml) and heated to 60° C. DBU (2.3 ml, 2 eq.) is added and the solution is stirred for 15 min. before adding further DBU (4.6 ml, 4 eq.) and again stirring for 15 min. Finally, DBU (4.6 ml, 4 eq.) is added a final time and the solution is stirred at 60° C. overnight and subsequently left to return to ambient temperature. 150 ml of AcOEt are added to this solution and extraction is carried out with HCl (1M). When the pH becomes basic, the organic phase is washed with water to neutrality. The extracted phase is dried over MgSO4, filtered and purified by flash chromatography (cyclohexane/AcOEt 99:1) in order to produce the compound 3 (1.22 g, 6.8 mmol, 87%), a colorless liquid.
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