B(F)(F)F.CCOCC.[CH:10]([O:17][CH2:18][CH3:19])([O:14][CH2:15][CH3:16])OCC.[CH3:20][O:21][C:22]([O:27][CH3:28])([CH3:26])[C:23](=[O:25])[CH3:24].C(N(CC)C(C)C)(C)C.C(=O)([O-])O.[Na+]>ClCCl>[CH2:18]([O:17][CH:10]([O:14][CH2:15][CH3:16])[CH2:24][C:23](=[O:25])[C:22]([O:27][CH3:28])([O:21][CH3:20])[CH3:26])[CH3:19]Boron trifluoride etherate (17.03 g, 120.0 mmol) was added drop-wise over 15 min to a cooled (−40° C.) solution of triethyl orthoformate (14.82 g, 100.0 mmol) in dichloromethane (50 ml). Stirring was continued for 10 min then the solution was transferred to an ice-water bath and stirred at 0° C. for 20 min. The mixture was cooled to −78° C., and 3,3-dimethoxy-2-butanone (6.61 g, 50.0 mmol) added followed by dropwise addition of N,N-diisopropylethylamine (19.39 g, 150.0 mmol) over 15 min. Stirring was continued for 1 h then the solution was poured onto a vigorously stirred mixture of saturated sodium hydrogencarbonate solution (500 ml) and dichloromethane (200 ml). The organic phase was separated, washed with ice-cold 1M sulfuric acid solution (2×500 ml) and ice-cold water (2×500 ml), dried over anhydrous sodium sulfate solution and evaporated to give 1,1-diethoxy-4,4-dimethoxypentan-3-one (11.72 g, 100%) as an orange oil.
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