[CH3:1][O:2][C:3](=[O:9])[CH2:4][C:5](=[O:8])[CH2:6][CH3:7].[Cl-].[Mg+2].[Cl-].N1C=CC=CC=1.[C:19](Cl)(=[O:22])[CH2:20][CH3:21].Cl>C(Cl)Cl>[CH3:1][O:2][C:3](=[O:9])[CH:4]([C:19](=[O:22])[CH2:20][CH3:21])[C:5](=[O:8])[CH2:6][CH3:7]5.21 g=5.02 ml (39.2 mmol) of 3-oxo-pentanoic acid methyl ester were dissolved in 30 ml of CH2Cl2, the solution was cooled to 2° C. and 3.81 g (39.2 mmol) of anhydrous magnesium chloride were added in small portions. Then, 6.21 g=6.34 ml (78.4 mmol) of pyridine were added to this suspension between 2° C. and 5° C., followed by 3.89 g=3.67 ml (41.2 mmol) of propionyl chloride. The reaction mixture was warmed up to RT and 1 hour later poured into crashed ice, acidified with HCl (25%) to pH 1-2 and extracted twice with Et2O. The organic phases were dried over magnesium sulfate, filtered and evaporated to give 7.62 g of title compound as light yellow oil. MS: 185.1 ([M−H]−).
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