Water → (+)-Nootkatone

Participants

Reaction Conditions

Reaction Steps

Sodium acetate trihydrate (0.22 g, 1.6 mmol) was added to a single-neck round bottom flask that had been fitted with a reflux condenser. A solution of the chloroenone Compound 8 (0.14 g, 0.54 mmol) in glacial acetic acid (4 mL) was injected into the flask, and the mixture was heated to 100° C. and held at that temperature for 2 hours. The reaction mixture was then cooled to room temperature, poured into cold water, and extracted with chloroform. The organic layer was then washed with successive portions of 2% aqueous KOH, 2 N HCl, NaHCO3, and brine, and then dried over MgSO4. The excess solvent was removed via rotary evaporator to provide nootkatone as a yellow oil (93%). The overall yield from β-pinene to nootkatone was 23% using path b, and 25% using path a, both of which are relatively high overall yields. Because the Oxy-Cope reaction and the methylation both provided the desired enantiomeric product, the enantiomeric purity of the final nootkatone product was little changed from that of the β-pinene starting product. Qualitatively, the fragrance of the synthesized nootkatone was identical to the fragrance of nootkatone derived from other sources. NMR data matched that previously reported for nootkatone: 1H NMR: (250 MHz, CDCl3), δ 5.77 (s, 1H), 4.75–4.72 (m, 2H), 2.62–2.43 (m, 1H), 2.41–2.22 (m, 4H), 2.09–1.87 (M, 3H), 1.46–1.38 (m, 1H), 1.12–1.10 (m, 4H), 0.98 (d, 3H).

Provenance & Evidence