Source:
A solution of the olefinic acid (0.499 g, 2.25 mmol) dissolved in benzene (20 ml, freshly distilled from calcium hydride) was stirred at 0 °C (ice bath) under nitrogen while oxalyl chloride (1.35 ml, 2.0 g, 15.75 mmol) was added dropwise. The ice bath 
was removed and the solution was stirred at room temperature for 2 hr. The solvent and excess reagent were removed in vacuo. The resulting orange oil was dissolved in benzene (2 x 5.0 mi, freshly distilled from calcium hydride) under nitrogen.
This solution was added dropwise at 0 °C (ice bath) to an anhydrous ethereal solution of diazomethane (50 ml, −20 mmol, predried over sodium metal) with vigorous stirring under nitrogen. The resulting solution was stirred at 0 °C for 1 hr and then at room temperature for 1.5 hr. The solvents and excess reagent were removed in vacuo.
Tetrahydrofuran (40 ml, freshly distilled from lithium aluminum hydride) and finely divided metallic copper powder (0.67 g) were added to the crude diazo ketone, sequentially. This suspension was vigorously stirred at reflux under nitrogen for 2 hr. The resulting suspension was allowed to stir at room temperature for an additional 14 hr. The solution was filtered into water (100 ml). The mixture was shaken vigorously for 5 min and then extracted with ether (3 x 50 ml). The combined ethereal extracts were washed with saturated sodium bicarbonate solution (4 X 40 ml), water (40 ml), and saturated sodium chloride solution (40 ml), dried (NaSO), and concentrated in vacuo to give 0.673 g of a crude brown oil. This crude oil was chromatographed on silica gel (67 g) in a 2-cm diameter column using 10% ether-90% petroleum ether to develop the column, taking 37-ml sized fractions. Fractions 11–16 gave 0.164 g (33%) of pure ketone product: mp 64-64.5° (from pentane); IR (CCl) 3095 (cyclopropyl CH) 
and 1755 cm (CO); NMR (CCl) δ 1.18 (s, 3H, CH) 1.03 (9, 3H, CH), 
0.97 (s, 3H, CH), and 0.90 ppm (s, 3H, CH). Anal. Calcd for CHO: C, 82.52; H, 10.16. Found: C, 82.61; H, 10.01.