To a mixture of (1RS,2SR,6RS,7SR)-10-oxatricyclo[5.2.1.02,6]dec-8-ene-3,5-dione (374 mg, 2.3 mmol) and phenanthroline (610 mg, 5 mmol) under an atmosphere of nitrogen is added dry toluene (20 ml) and 4′-chloro-4-methylbiphen-3-yllead triacetate (2.0 g, 3.4 mmol). The reaction mixture is heated at reflux for 3.5 hours, then cooled to room temperature, acidified to pH1 with 2N aqueous hydrochloric acid (20 ml), ethyl acetate (20 ml) added and the mixture is filtered to remove solids. The filtrate is poured into a separating funnel and extracted with ethyl acetate. The organic extracts are combined, dried over anhydrous magnesium sulfate, filtered and the filtrate is evaporated under reduced pressure. The crude product is purified by column chromatography on silica gel to give (1RS,2SR,6RS,7SR)-4-(4′-chloro-4-methylbiphenyl-3-yl)-10-oxatricyclo[5.2.1.02,6]dec-8-ene-3,5-dione.
