Ammonium Chloride → 4-Methoxy-3-(3,3,3-trifluoropropyl)benzaldehyde dimethyl acetal

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A solution of 229A (15.8 g, 60 mmol) in dry THF (120 ml) was added to magnesium turnings (4.1 g, 170 mmol) at RT. The mixture was heated to 60° C. for 5 min, which initiated an exothermic reaction. The heating bath was removed and the mixture was allowed to reflux gently. Upon subsidence of the reaction (approximately 5 min), the mixture was heated to reflux for an additional 20 min and then was allowed to cool to RT. The clear green supernatant was transferred via canula away from excess magnesium and into a separate flask containing copper (I) iodide (575 mg, 3.0 mmol) under a nitrogen atmosphere. To this mixture was added 1-iodo-3,3,3-trifluoropropane (15 g, 67 mmol) and the resulting mixture was allowed to stir for 16 h, during which time a thick white precipitate developed. Aqueous ammonium chloride solution, ethyl acetate, and hexanes were added, and the organic layer was dried over sodium sulfate. Evaporation followed by silica gel chromatography of the residue using 3:1 hexanes/ethyl acetate as eluant provided 7.7 g of a mobile, slightly yellow oil, which was a 6:1 (mol ratio) mixture of 229B and 4-methoxybenzaldehyde dimethyl acetal, as determined by proton NMR. This mixture was used without further purification.

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