Photooxygenation, chlorophylls

The formation of bacteriochlorins from chlorophyll derivatives has also been studied.8 The reduction product 16 of methyl 3 -oxorhodochlorin-l 5-acetate (see Section 1.2.2.) undergoes photooxygenation with singlet oxygen to yield finally a bacteriochlorin 17. 

Recently some quantitative analyses of the kinetics of type II direct and indirect photooxygenation reactions have been made. These dealt with the photooxygenation of 2,5-dimethylfuran7 61 and allylthiourea86 sensitized by xanthene dyes and chlorophyll, respectively, and with the... 

Beside xanthene dyes, methylene blue,127 porphyrins and por-phins,128-130 zinc-tetraphenylporphin,128 a-hydroxyanthraquinones in alkaline alcoholic or pyridine solutions,112,131 vitamin A, /9-carotene, hypericin, rubrene, 3,4-benzpyrene, 20-methylcholanthrene, chlorophyll, and many other compounds have been found to be sensitizers of photooxygenation reactions.70,132,133 Some groups of dyes, however, such as porphyrins and porphins containing transition metals (e.g., Co), azo dyes, cyanine dyes, and triphenylmethane dyes either did not show any or only very poor sensitizer capabilities in the photooxygenation of a-terpinene.128,134... 

Chlorophyll has been shown to be a sensitizer for type II photooxygenation reactions of various substrates.61135 A quantitative study has been made with allylthiourea as a substrate by Livingston and Owens.86... 

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