3-(1-Octen-1-yl)cyclopentanone.³ A 38.7-g quantity (0.150 mol) of chlorobis(η⁵-cyclopentadienyl)hydridozirconium, Schwartz's reagent, (Note 1) is weighed into an oven-dried, 250-mL, three-necked flask. The flask, equipped with argon inlet and exit tubes, a thermometer and magnetic stirrer, is placed in an ice/water cooling bath. Under an atmosphere of argon, 50 mL of dry tetrahydrofuran (Note 2) and 23.6 mL (0.16 mol) of freshly distilled 1-octyne (Note 3) are added. The ice/water cooling bath is used to keep the temperature between 15°C and 25°C during the addition. Stirring is continued in the ice bath for 2 hr to control a mildly exothermic reaction; then the flask is wrapped in aluminum foil and stirred overnight at room temperature (elapsed time is 18 hr). At this point, 10.9 mL (0.130 mol) of freshly distilled 2-cyclopentenone (Note 3) is added and the reaction mixture is chilled in an ice bath for 10 min. To the cooled reaction mixture a total of 3.34 g (0.0130 mol) of vacuum-sublimed (at 180°C), powdered, solid nickel acetylacetonate (Note 3),(Note 4) is added in three portions at 10-min intervals, keeping the temperature of the reaction mixture below 50°C (Note 5),(Note 6).

The mixture is stirred for 2 hr in the ice bath and for 2 hr at room temperature, then poured into a large Erlenmeyer flask containing 150 mL of 1 N hydrochloric acid and 200 mL of ice/water mixture. Hexane (400 mL) is added and the quenched reaction mixture is stirred for 30 min. Solid material is removed by vacuum filtration (Note 7) and the solids are washed with hexane (3 × 70 mL). The combined filtrates are transferred to a separatory funnel and the organic layer is removed. The aqueous layer (Note 7) is extracted with 300 mL of hexane and the extract is combined with the original organic layer. After the organic layer is washed successively with 300-mL portions of saturated sodium bicarbonate solution and brine, it is dried over sodium sulfate and concentrated under reduced pressure to give 24.8 g of crude product. The crude product is placed on a chromatography column prepared from 550 g of silica gel and hexane. The column is eluted with 2% ethyl acetate in hexane until 3.5 L of eluant has been collected. Then 4% ethyl acetate in hexane is used. The fractions containing the product (TLC) are combined and evaporated, finally under high vacuum, to afford 15.4 g (61%) of a very pale yellow liquid (Note 8). GC analysis of this product on an OV17 50-m capillary column (100°C to 200°C at 5°C/min) shows it to be 98.2% pure.

The material is distilled in a Kugelrohr apparatus at 0.15 mm and an oven temperature of 95–105°C to give 15.0 g (59% overall yield) of material with GC purity of 98.3% (Note 9).