Elimination reactions photochemical

Shimomura, O., and Johnson, F. H. (1979c). Elimination of the effect of contaminating CO2 in the lsO-labeling of the CO2 produced in biolu-minescent reactions. Photochem. Photobiol. 30 89-91. 

This approach offers unique opportunities for the generation of multi-functionalized cyclic 2-azadiene systems. A wide variation of the substitution pattern at the positions N-1 and C-6 can be determined by an appropriate choice of the aldehyde and amine. Various substituents can easily be introduced at the C-3 position via addition/elimination reactions on the sensitive imidoyl chloride moiety [24]. Upon reaction with bi-functional reagent, an adequately AT-protected 2(lH)-pyrazinone was elaborated into C-nucleoside analogues (Scheme 8). The desired skeleton and functionalities were obtained by oxidation-cyclization reaction followed by photochemical removal of the protective o-nitrobenzyl group [25]. 

Photochemical elimination reactions include all those photoinduced reactions resulting in the loss of one or more fragments from the excited molecule. Loss of carbon monoxide from type I or a-cleavage of carbonyl compounds has been previously considered in Chapter 3. Other types of photoeliminations, to be discussed here, include loss of molecular nitrogen from azo, diazo, and azido compounds, loss of nitric oxide from organic nitrites, and loss of sulfur dioxide and other miscellaneous species. 

The UV irradiation of the 4,5-dihydro-1,3,5-oxazaphosph(V)olene 39 leads to a cyclic elimination. Analogously to the thermal [5 + 3 + 2] cyclo elimination, the photochemical reaction generated nitrile ylides reacted with alkynes and alkenes to yield the 2/f-pyrrole 40 and the pyrrol-l-ine 41, respectively (equation 17)71. 

The degradation can be photochemically induced (a) homolytic or (b) heterolytic cleavage at the weaker bonds. The photolysis of the type (a) may lead to elimination reactions and the type (b) may lead to free radical formation. The point of bond cleavage may not be the seat for light absorption. The energy can migrate from unit to unit until it finds itself at the seat of reaction. 

Linearly connected polycyclic silanes are usually made by salt elimination reactions, whenever the cyclosilanyl alkali metal compound involved is stable enough. Otherwise, the photochemical cleavage of bis(cyclosilanyl)mercury compounds may be employed. An... 

Since most chemical reactions if carried to completion will result in deterioration of polymer properties, it is desirable to be able to ensure that all of the energy is dissipated in photophysical processes and to eliminate the photochemical reactions. However, in some cases, such as in the manufacture of photographic resists, it is desirable to maximize the photochemical effects. The polymer chemist is particularly concerned with the problem of how the relative efficiency of these various processes may be affected by the polymeric nature of the molecules he uses. 

Thermal and photochemical decompositions of sydnones differ depending on the substrate. The reactions are addition-elimination reactions involving various cyclic intermediates (Section 4.21.2.5). 

A set of photochemically promoted elimination reactions has been described for the d6 dithiolene complex CpCo(PBu3)(mnt) (47) and several closely related complexes 48-50 (152). Complexes 48 and 49 form by the reaction of the... 

For sometime, phosphinidines, monovalent organophosphorus species with the general formulation (R-P), have been postulated as reactive intermediates in the thermal and photochemical decomposition of several types of stable organophosphorus compounds. While not isolated as stable molecules, these monovalent species can be inferred on the basis of the isolation of products whose structures can be derived rationally from the postulation of such species, as well as on the mass spectra of the transient species themselves. We may view phosphinidines as the phosphorus analogues of nitrenes (R-N), highly reactive monovalent nitrogen species formed as transient intermediates in the thermal decomposition of azides and in the a-elimination reaction of A-tosylates. 

Photochemistry of Rhenium(I) Complexes A. Photochemical CO Elimination Reaction of a Re(I)... 

Figure 2. Photochemical isomerization and elimination reactions of Group 12 metalla-bis-nonaboranes.5...

Hexafluoroacetone has been a popular compound for further photochemical study" " Majer et al. have reported on the photolysis of alicyclic perfluoroketones and of chloropentafluoroacetone other work on fluorinated ketones has been reported by Pritchard et a/. - , by Phillips and Trotman-Dickenson , and by Schuster and Patel . Intramolecular elimination reactions in the photolysis of fluoroaldehydes have been discussed by Morris and Thynne and by Pritchard and Perona . Photolytic studies on other oxygen-containing halogen compounds have included chloroacetic acids , acetyl chloride , perfluoroacyl fluorides , CF3OF and CF3OOCF3 . 

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