Quinones, photochemistry

Brennan, J.F., and Beutel, J. (1969) Quinone photochemistry. II. The mechanism of photoreduction of 9,10-phenanthrenequinone and 2-tert-butyl-9,10-anthraquinone in ethanol. J. Phys. Chem. 73, 3245-3249. 

Horspooi, W. M. Enone cycioadditions and rearrangements Photoreactions of dienones and quinones. Photochemistry 200, 32, 74-116. 

Hurley, J. K., Castelli, R, Tollin, G. (1981). Chlorophyll-quinone photochemistry in liposomes Mechanisms of radical formation and decay, Photochem. Photobiol, 34 623. 

It is not the intention in the current account to present a comprehensive review of the literature since the early 1990s, but rather by citing selected pubHcations, to illustrate the breadth of interests in this area of quinone photochemistry and to provide further insight into the detailed mechanisms of these cycloaddition processes. 

Photo-de-diazoniation has found relatively little application in organic synthesis, as is clearly evident from the annual Specialist Periodical Reports on Photochemistry published by the Royal Society of Chemistry. Since the beginning of these reports (1970) they have contained a section on the elimination of nitrogen from diazo compounds, written since 1973 by Reid (1990). In the 1980s (including 1990), at least 90% of each report is concerned with dediazoniations of diazoalkanes and non-quinon-oid diazo ketones, the rest being mainly related to quinone diazides and only occasionally to arenediazonium salts. 

Through these works, Wan has conclusively demonstrated that the photodehydration of hydroxybenzyl alcohols is a general reaction, and a wide variety of quinone methides can be photogenerated and detected using this method. Quinone methide photogeneration via this method has been shown to have importance in the photochemistry of Vitamin B641,42 and in model lignins 43... 

A third reaction pathway for quinone methides generated following ESIPT to aromatic carbon (in addition to H-D exchange and cyclization) was observed following the examination of the photochemistry of 9-(2 -hydroxyphenyl)anthracene... 

Schuster, D. I. Krull, I. S. Photochemistry of unsaturated ketones in solution. XIX. Photochemistry of spiro[2.5]octa-4,7-dien-6-one. 2. Mechanistic aspects and the relationship to the photochemistry of quinone methides. Mol. Photochem. 1969, 1, 107-133. 

From the Contents J.L.R. Williams Photochemical Reactions of Polymers. M.B. Rubin Photochemistry of o-Quinones and -Diketones. L.B. Jones, V. K. Jones Photochemical Reactions of Cycloheptartrienes. C. V. Sonntag Strahlenchemie von Al koholen. 

Quinones undergo much interesting photochemistry. Triplet an-thraquinone lies 62.4 kcal above the ground state and readily abstracts hydrogen atoms from alcoholic solvents to yield semiquinone radicals.443... 

The quinones have excellent redox properties and are thus important oxidants in laboratoty and biological symlions. The presence of an extensive array of conjugated systems, especially the a, /(-unsaturated ketone arrangement, allows the quinones to participate in a variety of reactions. Characteristics of quinone reactions include nucleophilic substitution electrophilic, radical, and cycloaddition reactions photochemistry and normal and unusual carbonyl chemistry. 

Photochemistry of quinones (1,4-benzoquinone, duroquinone, 2,6-di-t-butylbenzo-quinone, etc.) radical anions was studied in detail [173a]. According to cyclic voltammetry data in various solvents, the quinones showed typical reversible two-wave voltammograms, corresponding to two successive one-electron transfers [(5.22), (5.23)] to the radical anion then to the dianion ... 

Photochemistry of Quinones and Hydroquinones in Solid 2-Hydroxypropylcellulose Films and on Filter Paper... 

The photochemistry of the methoxyhydroquinone A / methoxyquinone D couple in solution was extensively studied in our laboratories [14]. It involves, as for the reactivity of other simple quinones [12, 15], the formation of a neutral semiquinone radical which is able, in the low viscosity medium, such as fluid... 

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