[C:1]1([CH2:6][CH2:7][CH2:8][C:9](=[O:11])[CH3:10])[CH2:5][CH2:4][CH2:3][CH:2]=1.[CH3:12][Mg]Br.Cl>C(OCC)C>[C:1]1([CH2:6][CH2:7][CH2:8][C:9]([CH3:12])([OH:11])[CH3:10])[CH2:5][CH2:4][CH2:3][CH:2]=15-(Cyclopent-1-enyl)-2-pentanone (5.95 g; 39 mmol) in ethyl ether (6 ml) was added dropwise to a 3M solution of methylmagnesium bromide in the same solvent (17 ml; 51 mmol) during 15 minutes. After 2 hours at reflux, the mixture was cooled down to room temperature, poured into ice (20 g), acidified with 5N HCl (20 ml) and extracted with MTBE (60 ml). The aqueous phase was separated and extracted again with MTBE (2×100 ml). The combined organic phases were washed with saturated NaHCO3 (80 ml), H2O (80 ml), brine (80 ml), dried over MgSO4 and concentrated in vacuo. Bulb-to-bulb distillation (80° C./0.06 torr) yielded quantitatively 5.84 g of 5-(cyclopent-1-enyl)-2-methylpentan-2-ol containing 11% of 5-cyclopentylidene-2-methylpentan-2-ol.
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