(E)-6-(2,2,3-Trimethyl-cyclopent-3-enyl)-hex-4-en-3-one

Concepción Badía, Juan M. Castro, Pablo J. Linares-Palomino, Sofía Salido,

Joaquín Altarejos,* Manuel Nogueras and Adolfo Sánchez

Departamento de Química Inorgánica y Orgánica, Facultad de Ciencias Experimentales,Universidad de Jaén, 23071 Jaén, Spain.

Tel.: 34-953-002743, fax: 34-953-012141

E-mail: [email protected]

Received: 16 February 2004 / Accepted: 26 March 2004 / Published: 29 March 2004

Keywords: a-Campholenic aldehyde, ethyl 2-methylacetoacetate, aldol condensation.

Ethyl 2-methylacetoacetate (2) (727 mg, 4.53 mmol) was added to a stirred solution of NaH (184 mg, 4.60 mmol) in dioxane (25 mL). Then campholenic aldehyde (1) (707 mg, 3.72 mmol) was added and the mixture refluxed for 15 h. Then 2N HCl (15 mL) was added and the mixture extracted with Et₂O (3×15 mL). The combined organic layers were washed with 2N HCl (2×15 mL), saturated Na₂CO₃ (2×15 mL) and brine (3×15 mL). The organic phase was dried over anhydrous Na₂SO₄ and the solvent evaporated under reduced pressure to yield a residue (900 mg) which was purified by distillation under reduced pressure to give the title compound 3 (505 mg, 2.63 mmol, 58%). 

IR (neat, n, cm^-1): 1700, 1676 (CO), 3036, 1631, 984 (C=C).

¹H NMR (300 MHz, CDCl₃, d, ppm): 0.81 (3H, s, Me-2’), 1.00 (3H, s, Me’-2’), 1.10 (3H, t, J=7.4 Hz, H-1), 1.61 (3H, br s,  Me-3’), 1.77–2.42 (5H, m, H-5’, H-1’, H-6), 2.57 (2H, q, J=7.4 Hz, H-2), 5.22 (1H, br s, H-4’), 6.14 (1H, dt, J=15.8 Hz, 1.4 Hz, H-4), 6.85 (1H, dt, J=15.8 Hz, 7.3 Hz, H-5).

¹³C NMR (75 MHz, CDCl₃, d, ppm): 8.13 (C-1), 33.46* (C-2), 201.04 (C-3), 130.50 (C-4), 146.89 (C-5), 33.14* (C-6), 49.27 (C-1’), 46.90 (C-2’), 148.30 (C-3’), 121.45 (C-4’), 35.42 (C-5’), 19.72 (Me-2’), 25.80 (Me’-2’), 12.54 (Me-3’).

*These signals may be interchanged.

MS (70 eV, m/z): 206 (M⁺, 3%), 191 (M⁺–Me, 2), 177 (M⁺–Et, 4), 173 (5), 163 (4), 149 (M⁺–COEt, 5), 145 (7), 136 (7), 121 (11), 108 (C₈H₁₂⁺, 53), 98 (56), 93 (55), 79 (33), 67 (29), 57 (C₃H₅O⁺, 100), 41 (49). 

Acknowledgements:

We wish to thank the Ministerio de Ciencia y Tecnología for financial support (R+D Project PPQ2000-1665) and the Ministerio de Educación, Cultura y Deporte for a fellowship to J. M. Castro.

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