[Cl:1][C:2]1[CH2:6][C:5]([CH3:8])([CH3:7])[CH2:4][C:3]=1[CH:9]=O.[CH2:11]([O:13][C:14]([CH:16]=P(C1C=CC=CC=1)(C1C=CC=CC=1)C1C=CC=CC=1)=[O:15])[CH3:12]>C1C=CC=CC=1>[Cl:1][C:2]1[CH2:6][C:5]([CH3:7])([CH3:8])[CH2:4][C:3]=1/[CH:9]=[CH:16]/[C:14]([O:13][CH2:11][CH3:12])=[O:15]The following two procedures were adapted from Organic Preparations and Procedures Int., 29 (4), 471-498. A 500-mL single neck round bottomed flask equipped with a magnetic stirrer and nitrogen inlet was charged with 2-chloro-4,4-dimethylcyclopent-1-enecarbaldehyde (38 g, 240 mmol) in benzene (240 mL). To the solution was added ethoxycarbonylmethylene triphenylphosphorane (84 g, 240 mmol). The mixture was stirred for 14 h. After that time, the solvent was evaporated and the residue was triturated with hexanes (2 L) to extract the product away from the PPh3 by-products. The organic layer was dried over sodium sulfate and concentrated in vacuo. The residue was purified by column chromatography using a 100% hexane-1:1 hexane/ethyl acetate gradient to afford a 37% yield (20 g) of 110a.
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