Photooxygenation reactions table

This remarkable and synthetically useful selectivity apphes to both cis and trans non-symmetrically substituted alkenes. The regioselective photooxygenation reaction of some cis non-symmetrical alkenes and their regio-hmitations are shown in Table 5. 

However, the ft values were probably incorrectly taken from Bowen s work.150 If the ft values obtained by this author are used, Pa = 0.42 and j3s = 0.057 (see Table VII), a better agreement between the calculated slope (=0.14) and the observed slope is obtained. The range of experimental error in determining the individual ft values as well as in obtaining a reliable slope from the competitive photooxygenation reaction appears to be fairly large. The difference between the calculated and the experimental slope, therefore, does not allow the abandonment of the energy-transfer mechanism. 

Selective fomation of allylic hydroperoxides via singlet oxygen ene reaction 837 TABLE 2. Syn/anti regioselectivity in the photooxygenation of aUyUc alcohols 10- and 10-Z... 

Several other allylic alcohols with primary C-2 substituents have been epoxidized with good results (Table 3, entries 7-10 and 14). Epoxy alcohols have been obtained with 93-96% ee and when the catalytic version of the reaction is used, as in Table 3, entry 10, the yield is excellent. When the C-2 substituent is more highly branched, as in entries 11-13, there may be some interference to high enantiofacial selectivity by the bulky group, since the ee in two cases (entries 11 and 12) is 86%. Another example which supports this possibility of steric interference to selective epoxidation is summarized in equation (3). In this case, the optically active allylic alcohol (12) was subjected to epoxidation with bo antipodes of the titanium tartrate catalyst. With (+)-DIPT enantiofacial selectivity was 96 4 ( matched pair ), but with (-)-DIPT selectivity fell to only 1 3 ( mismatched pair ), a further indication that a secondary C-2 substituent can perturb the fit of the substrate to the active catalyst species. In the epoxidation of the allylic alcohol shown in elation (4), the epoxy alcohol is obtained in 96% yield and with a 14 1 ratio of enantiofacial selectivity. An interesting alternate route to the epoxide of entry 12 (Table 3) has been described, in which 2-r-butylpropene is first converted to an allylic hydroperoxide via photooxygenation and then, in the presence of the titanium tartrate catalyst, undergoes asymmetric epoxidation (79%... 

Table 5. Photostationary Ratios d2-77a d2-77a ) in the PET Reactions of d2-77a, Yields of 78a in the PET Photooxygenation of 77a,and Transient Absorption Maxima (Amax) Observed in Laser Flash Photolysis of 77a ... 

Photo-oxygenation is a quicker reaction than autoxidation and the relative rates for oleate, linoleate and linolenate are shown in Table 10.1. In autoxidation the methylene-interrupted diene system is significantly more reactive than the isolated double bond of a monoene but in photooxygenation the relative rates of oxidation are more closely related to the number of double bonds. On the basis of these values photo-oxygenation of methyl oleate can be 30000 times quicker than autoxidation and for the polyenes photo-oxygenation can be 1000-1500 times quicker. 

In comparison with the polymer bound sensitizers, the i micelle does not emit excimer emission. Furthermore, LCV is incorporated in micelle so that the loss of molecular motion in molecular aggregate state is not a serious drawback. However, side reaction of anthracene presumably photooxygenation at the 9, 10 position of anthracene is accelerated in micellar system. Results are summarized in Table 3. 

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