Experimental

14 g (19.9 mmol, 1.0 equivalents) of Compound 10 was dissolved in 100 mL of toluene. 1.2 g (49.8 mmol, 2.5 equiv) dry NaH was then suspended separately in another 100 mL of toluene. The NaH and Compound 10 mixtures were combined at room temperature and stirred for 10 minutes. 400 mL of toluene was then added, and the mixture was placed in an oil bath preheated to 140°C. The mixture was refluxed for 12 hours, then cooled to 0°C. During this reflux, compound 10 is deprotonated to form enolates 11 (major) and 12 (minor), which then underwent an intermolecular cyclization reaction to afford syn- and anti- 13.

After reflux, 30 mL of water was added slowly, and then the mixture was washed with 2M NaOH (4 x 150 mL), water (100 mL), and brine (100 mL). The organic layer was then collected and dried over MgSO4, then filtered and vacuum-concentrated to produce a yellow oil. The oil was then purified via flash chromatography on silica, using 20:1 hexanes: ethyl acetate, to produce the 3:1 mixture of syn-13 and anti-13.