[Li+].C[Si]([N-][Si](C)(C)C)(C)C.[CH3:11][O:12]/[CH:13]=[CH:14]/[C:15](=[O:17])[CH3:16].[CH3:18][C:19]1([C:22](Cl)=[O:23])[CH2:21][CH2:20]1>C1COCC1>[OH:23]/[C:22](/[C:19]1([CH3:18])[CH2:21][CH2:20]1)=[CH:16]\[C:15](=[O:17])/[CH:14]=[CH:13]/[O:12][CH3:11]LiHMDS (1M in THF, 845 mmol) was added dropwise to a solution of trans-4-methoxy-3-buten-2-one [51731-17-0] (845 mmol) in THF (2 L) at −78° C. After stirring for 15 min, a solution of 1-methyl-cyclopropanecarbonyl chloride [16480-05-0] (407 mmol) in THF (100 mL) was added. The resulting mixture was allowed to warm to rt over 2.5 h and then quenched by addition of a saturated solution of NH4Cl. The mixture was extracted with Et2O (2×). The combined organic phases were successively washed with a saturated solution of NaHCO3 and brine, dried (Na2SO4), filtered and concentrated. The residue was purified by silica gel column chromatography to afford the title compound as a yellow solid. ESI-MS: [M+H]+ 183; TLC: Rf=0.29 (9:1 Hex/EtOAc).
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