Cyclooctene photochemistry

Further studies on the photoisomerization of ci5-cyclohexene and cycloocta-1,3-diene have been reported. Again the work has focused on enantiodiffer-entiation. In this case a series of optically active chiral sensitisers (3) have been used under conditions where solvent and temperature have been varied. Some of the o-disubstituted and tetra substituted amide sensitisers afford mixtures with enantioisomeric excesses of 14%. The influence of pressure and temperature on the asymmetric photochemistry of cyclooctene has been reported. A variety of chiral sensitisers were used. Some of these are shown in (4). Other work has shown that aromatic phosphates, phosphinates and phosphines (e.g. 5-8) can also sensitise the isomerism of cyclooctene. Moderate stationary-state ratios were obtained. 

The photochemistry of Cr(CO)6 is similar to that of CpMn(CO)3. Upon photolysis of Cr(CO)6 in a hydrocarbon solution of either cis or /ra/w-cyclooctene, CO is lost in less than 100 ps (34-36) ( fast step in Scheme 2) forming the solvated Cr(CO)5S intermediate (3) which subsequently binds olefin in a second-order reaction (k3 step in Scheme 2) to fonn either (CO)5Cr(cw-cyclooctene) (cw-4) or (CO)5Cr(/rfl/w-cyclooctene) (trans-4) (22) These two steps have rate constants which fit the fast and "slow criteria demanded by the... 

A review of photochemistry carried out in ionic liquids and a monograph dealing with a variety of aspects of photochromism have been published Reviews have also highlighted the photosensitized enantiodifferentiating isomerization of cycloalkenes other than cyclooctene and the area of asymmetric photochemistry in general Mechanisms for the photosensitized isomerization of alkenes have been discussed and calculations have been carried out to assess the electron-transfer processes in the tetramethylethene-tetracyanoethene system ... 

Photolysis of Fe(CO)5 in the presence of olefins leads to formation of olefin complexes which exhibit catalytic properties. The complex [Fe(cyclooctene)2 ( 0)3] catalyzes isomerization of olefins in alkene solutions. The compound Fe(C2H4)(CO)4 which is formed in the gas phase by photolysis of Fe(CO)5 and ethylene catalyzes hydrogenation of 2114. Photochemistry of the following dinuclear complex of iridium(I) is interesting ... 

Srinivasan, R. and Brown, K.H., Organic photochemistry with high level (6.7 eV) photons duality of carbene intermediates from cyclic olefins, /. Am. Chem. Soc., 100,4602,1978. (Quantum yields quoted from this report have been adjusted to reflect the subsequentiy revised value for the E,Z isomerization of cyclooctene Schuchmann, H.-P., von Sonntag, C., and Srinivasan, R., Quantum yields in the photolysis of cis-cyclooctene at 185 nm,/. Photochem., 15, 159,1981.)... 

Inoue, Y., Matsuyama, E., and Wada, T, Pressure and temperature control of product chirality in asymmetric photochemistry. Enantiodifferentiating photoisomerization of cyclooctene sensitized by chiral benzenepolycarboxylates,/. Am. Chem. Soc., 120, 10687-10696, 1998. 

Inoue, Y, Kosaka, S., Matsumoto, K., Tsuneishi, H., Hakushi, T, Tai, A., Nakagawa, K., and Tong, L-H., Vacuum UV photochemistry in cyclodextrin cavities. Solid state Z-E photoisomerization of a cyclooctene-P-cyclodextrin inclusion complex,/. Photochem. Photobiol. A Chem., 71, 61-64,1993. 

Wada, T, Sugahara, N., Kawano, M., and Inoue, Y, First asymmetric photochemistry with nucleosides and DNA enantiodifferentiating Z-E photoisomerization of cyclooctene, Chem. Lett., 1174-1175, 2000. 

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