STEP 1: In a 25-ml Erlenmeyer flask is placed a stirring bar, 0.97 g (2.5 mmol) of benzyltriphenylphosphonium chloride, 0.57 g (2.5 mmol) of 9-anthraldehyde (Aldrich), and 3 ml of dichloromethane.
STEP 2: The mixture is stirred as vigorously as possible, and 1.3 ml of 50 per cent aqueous sodium hydroxide are added from a dropper at the rate of 1 drop per 7 seconds.
STEP 3: Stirring is continued for 30 minutes.
STEP 4: The mixture is transferred to a small separating funnel. Dichloromethane and water (10 ml of each) are used to rinse the flask.
STEP 5: The funnel is shaken and the organic layer removed. The aqueous layer is extracted with 5 ml of dichloromethane.
STEP 6: The dried (1 g of calcium chloride) organic layer is concentrated on a water bath, and the remaining solvent removed in a vacuum desiccator.
STEP 7: The resulting yellow semi-solid is recrystallised from 15 ml of propan-1-ol to give 0.52 g (74%) of thin yellow plates, m.p. 131133 °C; p.m.r. (CDC13, TMS) 6 7.3-8.5 (m, 14H, aromatic protons), 6.82 (d, 1H, J = 17 Hz, vinylic proton), 7.82 (d, 1H, embedded in the aromatic signal).
STEP 8: The J value of 17 Hz proves the structure to be (E).
STEP 9: The i.r. spectrum shows a strong band at 962 cm -1, indicative of an (E) configuration; the band at 680 cm -1 is indicative of a monosubstituted benzene ring.
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