[C:1](Cl)(=[O:6])[CH:2]=[CH:3][CH2:4][CH3:5].[CH3:8][C:9]1[C@H:14]2[C:15]([CH3:17])([CH3:16])[C@H:12]([CH2:13]2)[CH2:11][CH:10]=1>C(Cl)CCl.[Cl-].[Zn+2].[Cl-]>[CH2:4]([CH:3]1[C:12]2([C:15]([CH3:17])=[CH2:16])[CH2:13][CH:14]([C:9]([CH3:8])=[CH:10][CH2:11]2)[C:1](=[O:6])[CH2:2]1)[CH3:5]At 30° C., a mixture of 7.35 g of 2-pentenoyl chloride (62 mmol) and 1.7 g of zinc chloride (12 mmol, 0.2 eq.) in 85 ml ethylene chloride was treated dropwise within 20 min. with a solution of 19.4 g of (−)-alpha-pinene (142 mmol, 2 eq.) in 20 ml ethylene dichloride. The reaction mixture was then stirred at 30° C. for 30 min., then at 50° C. for 2 h, and finally at 80° C. for 1 h. After cooling, the reaction mixture was washed with aq. sat. NaCl soln. and aq. sat. NaHCO3 soln. The aq. phases were extracted with Et2O, dried (Na2SO4), and concentrated. FC (SiO2, hexane/Et2O 20:1) of the crude (26 g) gave 1.74 g (13%) of compound 2. The boiling point of the end product is 95° C. at 0.06 torr (0.08 mbar).
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