C1(C2CCCCCCCC2)BCCCCCCC1.[Cl:19][CH2:20][CH2:21][CH2:22][C:23]#[CH:24].NO.[CH2:27]([Zn:29]CC)[CH3:28].CCCCCC>C1COCC1>[CH2:27]([Zn:29][CH:24]=[CH:23][CH2:22][CH2:21][CH2:20][Cl:19])[CH3:28]
A solution of 9-borabicyclononane (0.24 g, 2.0 mmol) in THF (5 mL) was added dropwise to a solution of 5-chloro-1-pentyne (0.21 g, 2.0 mmol) in THF (5 mL). After 1 h, the solvent was removed at reduced pressure. The resultant vinyl boron derivative was dissolved in toluene (5 mL) and aminoalcohol 1 (0.05 g, 0.17 mmol) prepared as in Example 1 was added. Then 1 M diethylzinc in hexane (3 mL, 3 mmol) was added via syringe at −78° C., forming ethyl-(5-chloro-1-pentenyl)zinc in situ. The dry ice bath was replaced with a wet ice bath and immediately a solution of isobutyraldehyde (0.17 g, 2.4 mmol) in hexane (5 mL) was added dropwise. After 1 hour the wet ice bath was removed and the mixture was stirred at room temperature for 8 h. Acetic anhydride (500 μL) was added and the mixture was allowed to stand overnight. GC analysis at 130° C. on Cyclodex B revealed that trans-3-acetoxy-2-methyl-8-chlorooct-4-ene had been formed in 92% enantiomeric excess.
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