To a solution of tert-butyl-[[5-(methoxymethoxy)-2-methyl-phenyl]methoxy]-dimethyl-silane (Intermediate 174, 0.3 g, 1 mmol) in hexane (5 ml), BuLi (1.6M in hexane, 0.9 ml, 1.4 mmoli) was added at room temperature. The reaction mixture was stirred for 2 h and then added dropwise at −30° C. to a suspension of CeCl3 (0.37 g, 1.5 mmoli) in dry THF (5 ml) that was previously stirred at room temperature overnight. After 45 min at −30° C., cyclobutanone (0.07 g, 1 mmoli) dissolved in THF (1 ml) was added. The reaction was stirred at the same temperature for and then quenched with ammonium chloride (20 ml) and extracted with Ethyl Acetate (2×20 ml). Combined organic layers were dried over Na2SO4 and evaporated under vacuum to afford a colorless oil that was purified by flash chromatography (Biotage system) on silica gel using a 25 g SNAP column and cyclohexane to cyclohexane/ethyl acetate 75:25 as eluents affording the title compound (0.05 g) as a colorless oil.
