Sensitizer photooxygenation

Some unusual pyridazine syntheses were reported. A dye-sensitized photooxygenation reaction of ribofuranosyl furans gave a new entry to pyridazine C-nucleosides 14... 

Wittig reaction of 10 with pentyl phosphonium salt in the presence of NaH gave Z-olefin 11 selectively. Dye-sensitized photooxygenation of 11 proceeded exclusively to give the endoperoxides 12a and 12b in almost quantitative yield as a roughly 1 1 mixture of two diastereomers. 

The oxaziridine ring system has been formed by the oxidation of C=N double bond . The two-step synthesis of iV-phosphinoyloxaziridines 16 from oximes 15 was described (equation 7) . Irradiation of hydroperoxynitrones 18, prepared by dye-sensitized photooxygenation of 2-methoxyfuran in the presence of oximes 17, led to fraw -oxaziridines 19 in yields up to 89% (equation 8) ". ... 

Dye-sensitized photooxygenation of oxazoles (242) in aprotic solvents with 650 W halogen lamp leads to unstable 1,2,4-dioxazolines (244) via intermediate cyclic peroxides (243) (Scheme 49) <90JCS(Pl)10n, 91JCS(P2)1085>. 

Tetraphenylporphyrin-sensitized photooxygenation of 1,2-disubstituted digermirane (383 X = CH2) and 1,2,3-disubstituted azadigermiridine (383 X = NPh) (Equation (36)) leads to corresponding cyclic peroxides <92CC457>. 

The DCA-sensitized photooxygenation of electron-rich substrates is markedly accelerated (3-10 times) by the addition of biphenyl (BP), which acts as an effective one-electron carrier from the substrate to the excited state of the acceptor (equations 6 and 7). 

The stereochemistry of the ET oxygenation of both stereoisomers of 87 allows insight into the geometry of the transient intermediate. Thus, DCA-sensitized photooxygenations of cis- and tram-fn gave 68 32 and 41 59 mixtures of cis- and trans-SS, respectively (equation 91 and Table 18). These results are in agreement with the intermediacy of open intermediate hke 86, and with the fact that rotation around the Si—O bonds is fairly competitive with the collapse to 88. 

Arteflene (5) >7 steps (A) Dye-sensitized photooxygenation (Ene reaction) 35 nM (Kl) 20 mgkg Metabolism and toxicity studies completed prior to phase 2 clinical trials 14... 

The methylene-blue sensitized photooxygenation of 164 yields the isolable dioxetane 165 (70%), the first of its kind to be isolated from an imidazole, presumably via the sequence of Schemes 10 and 26. Some of its reactions are illustrated (Scheme 44). ... 

Photoinduced reactions of benzo[ ]phenazine 32 are governed by the presence of low-lying 7t Jt" states, and include both [4-1-4] dimerization and self- or exogenously sensitized photooxygenation (Equation 3) <1995H(40)577>. 

Oa-Consumption, in milliliters of 02 per minute, in Rose Bengal-Sensitized Photooxygenation of a-Terpinene in Different Solvents as a Function of Temperature (from ref. 124) ... 

Diaryl- and tetraaryl-substituted furans such as tetraphenylfuran (384) for example, yield generally cw-diaroylethylenes such as 380, probably via intermediate ozonide formation.257 Secondary reactions seem to depend very much on the nature of the solvents. Thus, cis-dibenzoylstilbene (380) has been observed by direct photooxygenation of 384 in CS2 as well as by methylene blue-sensitized photooxygenation of 384 in methanol.257,258 However, when the latter reaction was carried out in acetone, epoxide 386 and the enolbenzoate 387 were obtained.258... 

Acenaphtho[l,2-c]furan 317 has been obtained in high yield through sensitized photooxygenation of cyclopentadienol 316 and subsequent treatment with acid hemiketals of the type described above are involved. The rhodium complex pathway to 317 was unsuccessful oxidation of 319,... 

C. Kinetics of photoperoxidation reaction. In the sensitized photooxygenation by Type lib mechanism the 02 (JAg) acts as dienophile and adds to give the endoperoxide in concerted addition reaction similar to Diels-Alder... 

D.L. Kearn and A.U. Khan, Sensitized photooxygenation reactions and the role of singlet oxygen , Photochem. Photobio., 10, 1969, 193. 

Benzo[c]furans undergo very rapid photooxidation. 1,3-Diphenylbenzo[c ]furan yields the oxide (368) on sensitized photooxygenation in ether at -50 °C. Reduction of the oxide with potassium iodide in acetic acid affords 1,2-dibenzoylbenzene and reaction with methanol supplies the hydroperoxide (369). 

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