[Cl:1][C:2]1[O:3][CH:4]=[C:5]([CH2:7][OH:8])[N:6]=1.[CH3:9][S:10](Cl)(=[O:12])=[O:11].C(N(CC)CC)C.[Cl-].[NH4+]>ClCCl>[CH3:9][S:10]([O:8][CH2:7][C:5]1[N:6]=[C:2]([Cl:1])[O:3][CH:4]=1)(=[O:12])=[O:11]A solution of (2-chloro-1,3-oxazol-4-yl)methanol (5 g, 37.44 mmol, 1 eq, prepared according to the method described in Tetrahedron Lett. (2004), 45, 3797-3802) in dichloromethane (250 ml) is reacted with methanesulfonyl chloride (3.19 ml, 41.19 mmol, 1.1 eq) in the presence of triethylamine (5.79 ml, 41.19 mmol, 1.1 eq) at 0° C. After 1 h 30, the mixture is poured into a saturated solution of ammonium chloride and extracted twice with dichloromethane. The organic layer is dried over magnesium sulfate, filtered and concentrated under vacuum to afford 7.9 g of (2-chloro-1,3-oxazol-4-yl)methyl methanesulfonate i59. This product is used in the next step without further purification or analysis.
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