[C:1]([C:5]1[CH:6]=[C:7]([CH:10]=[C:11]([F:13])[CH:12]=1)C=O)([CH3:4])([CH3:3])[CH3:2].C1(C)C(S(O)(=O)=O)=CC=CC=1.C(N(CC)CC)C.[CH:32](OC)([O:35][CH3:36])[O:33][CH3:34]>CO>[C:1]([C:5]1[CH:12]=[C:11]([F:13])[CH:10]=[C:7]([CH:32]([O:35][CH3:36])[O:33][CH3:34])[CH:6]=1)([CH3:4])([CH3:2])[CH3:3]3-tert-Butyl-5-fluoro-benzaldehyde (252 g, 1.4 moles) was dissolved in methanol (4 vol, 1000 ml) and trimethyl orthoformate (1 vol, 252 ml). Toluenesulfonic acid (3.4% w/w, 6 g) was added in one portion and the resulting solution stirred at rt for 1 hour. Triethylamine (0.12 vol, 30 mL) was added and the reaction concentrated to an oil, and then re-suspended in ethyl acetate (3 L) and NaHCO3 (aq. sat., 1 L) and water (1 L) with vigorous mixing. The organic phase was washed with additional water (1 L), polish filtered and then concentrated to provide an orange oil (311.2 g, 98.5%), used directly in the next reaction.
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