Br[CH2:2][C:3]#[C:4][CH3:5].[H-].[Na+].[OH:8][C:9]1([C:20]2[CH:25]=[CH:24][CH:23]=[CH:22][C:21]=2[CH3:26])[CH2:12][N:11]([C:13]([O:15][C:16]([CH3:19])([CH3:18])[CH3:17])=[O:14])[CH2:10]1.O>CN(C)C=O>[CH2:2]([O:8][C:9]1([C:20]2[CH:25]=[CH:24][CH:23]=[CH:22][C:21]=2[CH3:26])[CH2:12][N:11]([C:13]([O:15][C:16]([CH3:19])([CH3:18])[CH3:17])=[O:14])[CH2:10]1)[C:3]#[C:4][CH3:5]1 ml (11.4 mmol) of 1-bromo-2-butyne is added to a suspension of 1.4 g (34.2 mmol) of sodium hydride at 60% in 14 ml of dimethylformamide cooled beforehand to 0° C. After stirring for 1 h, 3 g (11.4 mmol) of tert-butyl 3-hydroxy-3-o-tolylazetidine-1-carboxylate in 20 ml of dimethylformamide are added dropwise and the reaction mixture is then stirred for 1 h 30. After hydrolysis with water and with a saturated aqueous solution of ammonium chloride, the reaction medium is extracted with a 1/1 heptane/ethyl acetate mixture. The organic phase is dried over sodium sulphate, filtered and concentrated. The residue obtained is purified by silica gel chromatography, elution being carried out with a 80/20 heptane/ethyl acetate mixture. 2.9 g of tert-butyl 3-but-2-ynyloxy-3-o-tolylazetidine-1-carboxylate are obtained in the form of a yellow oil with a yield of 81%.
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