[O:1]=[CH:2][C:3]1[CH:11]=[CH:10][C:7]([O:8][CH3:9])=[C:5]([OH:6])[CH:4]=1.CN(C)C=O.C(=O)([O-])[O-].[K+].[K+].[CH2:23]1[CH:27]2[CH2:28][CH:29](Br)[CH:25]([CH2:26]2)[CH2:24]1>O>[CH:25]12[CH2:26][CH:27]([CH2:28][CH2:29]1)[CH2:23][CH:24]2[O:6][C:5]1[CH:4]=[C:3]([CH:11]=[CH:10][C:7]=1[O:8][CH3:9])[CH:2]=[O:1]Isovanillin (50 g, 0.328 mol) is placed in a 1 liter round bottom flask which is equipped with a stir bar and reflux condenser and is charged with 500 ml of dimethylformamide, Potassium carbonate (45.3 , 0.328 mol) is added to the reaction mixture which is heated to 80° C. At this temperature exo-2-bromonorbornane (12.57 g, 0.072 mol, 0.219 equivalents) is added and the reaction mixture is heated to 120° C. for 48 hours. The reaction is then cooled to room temperature and poured into 300 ml of water. The aqueous layer is extracted with ethyl ether (3×100 ml). The ethereal layer is washed with 1N sodium hydroxide solution. (4×100 ml), water (3×100) ml) and saturated sodium chloride solution (3×100 ml). The organic layer is dried over anhydrous magnesium sulfate, filtered and concentrated in vacuo to yield 15.47 g of a green/brown oil. The crude product is purified with flash chromatography using a gradient eluent system of ethyl acetate/hexane [10% ethyl acetate/hexane →20% ethyl acetate/hexane] to yield 7.76 g (14.4%) of the aldehyde as a white solid. MP: 75.5° C.-79.5° C.
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