Reaction photoallylation

For example, allylic silanes react with photoexcited iminium salts by ET resulting in photoallylation. ° Key steps in such reactions are the cleavage of the C—Si... 

Similar to ketones, quinones have also been known for a long time to undergo PET processes with several donors such as aromatic hydrocarbons, olefins and amines etc. [10b, 11]. It is pertinent here to illustrate one of the synthetically important quinone-olefin [186] reactions which has been utilized for the preparation of Benz (a) anthracene 7,12-dione derivatives (237). In the present example, the excited state of naphthaquinone (234) reacts with ethene (235) to give 236, provided the electron transfer is thermodynamically allowed (ca. AGet < 0). In the follow up processes, (236) is transformed to (237) in 30-50% yield. Another report from the same group has described [187] a novel method of photoallylation of naphthaquinone by allyl stannane. 

The product distribution in flie photoreactions of organosilicon compounds with electron-deficient compounds often depends on the reaction media. " In nonpolar solvents, the photocycloaddition of allylsilanes to electron-deficient aromatic compounds occurs to give cyclobutanes via exciplex intermediates. In contrast, photoallylation of the aromatic compounds or the carbonyl group takes place via free radical ions in polar solvents. Some examples are shown in Schemes 5 and 6. 

The photoreaction of l,l-dicyano-2-phenylefliene with allylsilane in the presence of phenanthrene in acetonitrile affords 5,5-dicyano-4-phenyl-l-pentene in good yield. Phenanthrene acts as a redox sensitizer in this process and allylation occurs at the position P to the cyano group. On the other hand, a similar photoallylation reaction of cyclo-... 

Arakawa, R., Lu, J., Mizuno, K., Inoue, H., Doe, H., Matsuo, T. (1997) On-line Electrospray Mass Analysis of Photoallylation Reactions of Dicyanobenzenes by Allylic Silanes via Photoinduced Electron Transfer. Int. J. Mass Spectrom. Ion Proc. 160 371-376. 

The same on-line photochemical ESI-MS methodology was employed in the analysis of photoallylation reactions of dicyanobenzene (DCB) by aUyhc silanes via photoinduced electron transfer [48]. Brum and Dell Orco [32] reported on investigations of the photolysis of a substituted triphenylethylene derivative using the reactor depicted in Figure 5.4. The approach allowed the monitoring of the parent species and five relevant reaction products simultaneously. The rate constants for photoconversion could be derived from the time-ion current data. Herein, Schuster, and coworkers used ESI-MS to study offline some photoadditions to Cgo [49]. 

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