5-Methoxy-7,7-dimethyl-1,9(E),11-dodecatrien-3-one

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Scheme

The triene alcohol [1] was oxidized to the vinyl ketone under Swern conditions [2] as follows. To a stirred solution of DMSO in dry CH₂Cl₂ at -78 ƒC under Ar, trifluoroacetic anhydride was added dropwise via a syringe. The mixture was stirred for 15 minutes, then the triene alcohol in dry CH₂Cl₂ was added. Stirring was continued for an additional 30 minutes while maintaining the temperature below -50 ƒC, after which Et₃N was added and the reaction allowed to warm to room temperature. Following dilution with pet ether and addition of 1N aq NaOH, the mixture was stirred an additional 4 hours. The reaction was extracted with pet ether and the combined organic layers washed with sat aq NaHCO₃, NH₄Cl, and sat aq NaCl, then dried over Na₂SO₄ and concentrated to give the triene ketone as a colorless oil in 44 percent yield.

¹H NMR (CDCl₃): d: 6.4 - 6.15 (m, 3H), 5.98 (dd, J = 14.8, 10.4Hz, 1H), 5.81 (dd, J = 10.2, 1.2Hz, 1H), 5.68 (dt, J = 15.0, 7.5Hz, 1H), 5.04 (d, J = 16.7Hz, 1H), 4.91 (d, J = 10.0Hz, 1H), 3.78 (m, 1H), 3.25 (s, 3H), 2.86 (dd, J = 15.8, 5.4Hz, 1H), 2.57 (dd, J = 15.8, 6.8Hz, 1H), 1.99 (dd, J = 10.4, 3.3Hz, 1H), 1.96 (dd, J = 10.4, 3.5Hz, 1H), 1.45 (dd, J = 14.6, 8.0Hz, 1H), 1.21 (dd, J = 14.6, 2.9Hz, 1H), 0.89 (s, 3H), 0.87 (s, 3H).

IR (CDCl₃): 2955, 2925, 2825, 1670, 1610, 1460, 1400, 1365, 1190, 1090, 1005, 880.

MS (m/e): 236 (M⁺, 4), 221, 204, 167, 156, 137, 113, 108 (100), 99, 93, 55.

1. Smith, D. 5-Methoxy-7,7-dimethyl-1,9(E),11-dodecatrien-3-ol, Molecules 1997, 2, M37.
2. Omura, K.; Sharma, A. K.; Swern, D., J. Org. Chem. 1976, 41, 957.

Sample Availability: No sample available.

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