[CH3:1][C:2]1[CH:20]=[C:19]([O:21][Si](C(C)C)(C(C)C)C(C)C)[CH:18]=[C:17]([CH3:32])[C:3]=1[CH2:4][C:5]1[CH:6]=[CH:7][C:8]([O:13][CH2:14][O:15][CH3:16])=[C:9]([CH:12]=1)[CH:10]=[O:11].CCCC[N+](CCCC)(CCCC)CCCC.[F-]>C1COCC1.CCOC(C)=O.O>[OH:21][C:19]1[CH:18]=[C:17]([CH3:32])[C:3]([CH2:4][C:5]2[CH:6]=[CH:7][C:8]([O:13][CH2:14][O:15][CH3:16])=[C:9]([CH:12]=2)[CH:10]=[O:11])=[C:2]([CH3:1])[CH:20]=1
To a solution of 5-(2,6-dimethyl-4-triisopropylsilanyloxybenzyl)-2-methoxymethoxy-benzaldehyde (1.4 g, 3.07 mmol) in THF (15 mL) was added TBAF (1 M, 3.68 mL) at 0° C. After stirring at r.t. for 2 h, the reaction mixture was diluted with EtOAc and water. The water layer was extracted with EtOAc and the combined organic extracts were dried (MgSO4), filtered and concentrated. The residue was purified by column chromatography on silica gel (ethyl acetate-hexanes; 1:9) to afford 5-(4-hydroxy-2,6-dimethylbenzyl)-2-methoxymethoxybenzaldehyde (590 mg, 64% for two steps): 1H NMR (200 MHz, CDCl3): δ 10.45 (s, 1H), 7.54 (s, 1H), 7.27 (m, 1H), 7.09 (m, 1H), 6.56(s, 2H), 5.25 (s, 2H), 3.92 (s, 2H), 3.50 (s, 3H), 2.16 (s, 6H). TLC conditions: Uniplate silica gel, 250 microns; Mobile phase=ethyl acetate-hexanes (1:9); Rf=0.68.
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