Aluminum isopropoxide → (2RS,3E,6R)-6,10-dimethyl-3,9-undecadien-2-ol

Beteiligte Stoffe

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Reaktionsschritte

A flame-dried 1 L 3-necked flask, fitted with a 30 cm Vigreux column topped with a distillation head, an argon inlet tube and a magnetic stirring bar, was charged with 36.8 g (0.189 mol) of (3E,6R)-6,10-dimethyl-3,9-undecadien-2-one (GC purity 93.6%), 500 mL of iospropanol and 40.0 g (0.196 mol) of aluminum isopropoxide. The reaction mixture was stirred and heated to gentle reflux under argon. Acetone was allowed to distill off at a rate of about 30 drops/min. While maintaining a head temperature of ca. 80° C. After 3.5 hours the reaction was shown by GC to be almost complete with 5% of starting material remaining. The reaction was cooled in an ice bath and the pressure was reduced to ca. 54 mmHg. Isopropanol was distilled off at a head temperature of 30° C.-31° C. until the reaction mixture was concentrated to a volume of about 200 mL. The residual oil was cooled in an ice bath, 200 mL of 2N HCl were carefully added with stirring and the mixture was poured into a separatory funnel containing 200 mL of ether. An additional 200 mL of 2N HCl were added to dissolve some remaining white solid material. The layers were separated and the aqueous phase was extracted with 2×200 mL of ether. The combined organic layers were washed successively with 200 mL of sat. NaHCO3 -solution and 200 mL of brine, dried over MgSO4, filtered and concentrated on the rotovapor. The residue was dried at 0.1 mm for 30 minutes to afford 38.1 g (102.6%) of (2RS,3E,6R)-6,10-dimethyl-3,9-undecadien-2-ol as a light yellow liquid. GC analysis indicated a purity of 94.6%. This material was used as is in Example 2.

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