J . Am. Chem. SOC.1992, 114, 5073-5080
gel, hexane-ethyl acetate, 4:l)gave 31 (186 mg, 34%), 32 (26 mg, 5%), 34 (124mg, 23%), and 33 (57 mg, 10%). 4 43'-Chloropropyl)-4-cyano-ll-oxo-l0-oxatricycl~3.3.2.l]undeca2,7-diene (13). 9b (244mg, 1.25 mmol) in benzene (80 mL) and furan (255 mg, 3.75 mmol) was irradiated through uranyl glass for 18 h. Removal of solvent in vacuo gave 286 mg of an oil. Flash chromatography (silica gel, hexane-ethylacetate, 5 : l ) followed by preparative TLC (silica gel, hexane-ethylacetate, 1:l) gave 13 (70mg, >85% pure,
