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J. Am. Chem. SOC.1988, 110, 198-204
diated on a merry-go-round apparatus at 25 OC. Direct irradiations were carried out through a K2C0, ( 1.3%)-K2Cr04(0.13%) filter solution (mainly 3 13 nm). Benzophenone-sensitized irradiations were done through a phenanthrene solution (5 g/L) in methanol (>350 nm) or through a glass filter (Riko U-360, mainly 366 nm). The reaction mixtures were analyzed by HPLC, using naphthalene or m-terphenyl as the internal standard. A small amount of isomeric olefin impurities
involved in the starting material was carefully checked by HPLC: the purities of the rt- and t-isomers were >99.99% and those of the other isomers were >99.4%. When necessary, corrections were made in the calculation of the quantum yields. In all cases the reaction was stopped at a small conversion (
