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The crude ethyl 15-oxocyclopentadeca-3E,11E-dienecarboxylate (prepared as described above) was treated with ethanol (10 ml) and 3N aqueous hydrochloric acid (20 ml) and heated to reflux for 20 hours. The solution was cooled and diethyl ether and water were added. The layers were separated and the organic fraction was dried with magnesium sulfate, filtered and evaporated to provide a brown oil which was purified by column chromatography (10% diethyl ether/hexane) to afford cyclopentadeca-4E,12E-dien-1-one (0.50 g, 17% yield from diethyl hexadeca-4E,12E-diene-1,16-dioate). C15H24O (220.36 g/mole). 1HNMR (500 MHz, CDCl3): 1.15 (m, 4H), 1.34 (m, 4H). 1.97 (m, 4H), 2.24 (m, 4H), 2.45 (m, 4H), 5.30 (m, 2H), 5.39 (m, 2H) ppm. 13CNMR (125 MHz, CDCl3): 26.7, 27.4, 28.4, 31.2, 42.8, 129.2, 131.3, 210.4 ppm. IR (νmax(cm−1)): 2990, 2950, 2910, 2850, 1720, 1440, 1400, 1360, 1080, 980, 720. MS (m/z): 220(M+), 177, 163, 149, 135, 121, 109, 95, 81, 67, 55, 41.

1. temperatureheated
2. temperatureto reflux for 20 hours
3. temperatureThe solution was cooled
4. customThe layers were separated
5. dry with materialthe organic fraction was dried with magnesium sulfate
6. filtrationfiltered
7. customevaporated
8. customto provide a brown oil which
9. customwas purified by column chromatography (10% diethyl ether/hexane)