[C:1]([O:4][C:5](=O)[CH3:6])(=[O:3])[CH3:2].[CH3:8][C:9]1([CH3:21])[C:13]([CH3:14])=[CH:12][CH2:11][CH:10]1[CH:15]=[CH:16][CH2:17]C(O)C.O>CN(C)C1C=CN=CC=1.CC(OC)(C)C>[CH3:8][C:9]1([CH3:21])[C:13]([CH3:14])=[CH:12][CH2:11][CH:10]1[CH:15]=[CH:16][CH2:17][CH:5]([O:4][C:1](=[O:3])[CH3:2])[CH3:6]50 g (0.48 mol) of acetic anhydride was added dropwise to the solution of 78.6 g (0.40 mol) of 5-(2,2,3-trimethylcyclopent-3-enyl)pent-4-en-2-ol and 5.0 g of 4-dimethylaminopyridine in 150 ml of MTBE. The reaction mixture was stirred at 50-55° C. for 1 hour, treated with 0.5 l of water and extracted with 3×150 ml of hexane. The combined organic layers were neutralized with aqueous potassium hydrogen carbonate solution, washed with water, dried (MgSO4) and evaporated in vacuo. The residue (102 g) was distilled at 80-81° C./0.2 Torr to give 89.8 g (95% yield) of acetic acid 5-(2,2,3-trimethyl-cyclopent-3-enyl)pent-4-en-2-yl ester.
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