Methyl Benzoate → rel-(1R,4E,pR)-Cyclooct-4-enol

(E)-cyclooct-4-enol was synthesized from (Z)-cyclooct-4-enol using a modification of a previously reported protocol (Royzen, M. et al. J. Am. Chem. Soc. 2008, 130, 3760-3761). Briefly, 1 gram of cyclooctenol (2) and 1.1 g methyl benzoate sensitizer was added to 250 mL solvent (9:1 Ether:Hexanes) in a 500 mL quartz reaction vessel (Southern New England Ultraviolet Company). No attempt to degas the solution was made. The vessel was irradiated with 254 nm light in a Rayonet RPR-100 UV reactor (Southern New England Ultraviolet Company) under constant stirring. At 30 minute intervals, the irradiation was stopped and the entire solution was passed through a column packed with silver nitrate (10%) impregnated silica (commercially available from Aldrich). The solution that passes through was then transferred back into the quartz flask and irradiation was continued. After 6 hours the irradiation was stopped and the silica was added to a solution of ammonium hydroxide and stirred for 5 minutes after which ether was added and stirring continued for 5 more minutes. After stirring the ether phase was decanted, washed with water, dried with magnesium sulfate, and evaporated yielding trans-cyclooctenol (40%) as a mixture of isomers as previously reported. The isomers were separated by column chromatography (1:1 Ethyl Acetate Hexanes) and verified by proton NMR using the previously reported proton NMR spectra (Royzen, M. et al. J. Am. Chem. Soc. 2008, 130, 3760-3761) The major isomer (more polar isomer) was used for the synthesis of (E)-cyclooct-4-enyl 2,5-dioxopyrrolidin-1-yl carbonate.