Alkenes intrazeolite photooxygenation

The majority of intrazeolite photooxygenations have been conducted in NaY,84 85 however, one study in the pentasil zeolite ZSM-5 demonstrates that steric confinement effects can play important roles.84 A comparison of the reactions of a series of tri-substituted alkenes in isooctane, NaY, and in ZSM-5 is given in Fig. 21. The reactions... 

Stratakis, M., Nencka, R., Rabalakos, C., Adam, W. and Krebs, O. (2002). Thionin-sensitized intrazeolite photooxygenation of trisubstituted alkenes substituent effects on the regioselectivity as probed through isotopic labeling. J. Org. Chem. 67, 8758-8763... 

Wagnerova Class I intrazeolite photooxygenation, 233-253 of alkanes, 234—235 of alkenes, 235-243 regiochemistry, 236, 237, 243, 244 steric confinement effects, 237/ 246-247 Wagnerova Class II intrazeolite photooxygenation, 253-261 of alkanes, 256/ 258-259 of alkenes, 253-257, 253/ 256/ charge-transfer (CT) complexes in, 253-254, 255, 257... 

For the achievement of mass balances in intrazeolite photooxygenation reaction, >80%, loading levels of 0.1-0.3 adsorbed molecules per zeolite supercage have been successfully used in the past. However, the recent observation by Pace and Clennan, that replacing the solvent hexane with peril uorohexane was very crucial for the efficiency of the reaction, allowed the zeolite medium to be used for preparative scale photooxygenation reactions (500 mg of alkene), without loss of the product selectivity or the reduction of the mass balance. 

Type 1 intrazeolite photooxygenation of alkenes has been also reported to give mainly allylic hydroperoxides (Scheme 42). In this process, the charge transfer band of the alkene—O2 complex within Na-Y was irradiated to form the alkene radical cation and superoxide ion. The radical ion pair in turn gives the allylic hydroperoxides via an allylic radical intermediate. On the other hand, for the Type II pathway, singlet molecular oxygen ( O2) is produced by energy transfer from the triplet excited state of a photosensitizer to 02. 

Additionally, in order to elucidate the energy reaction profile in the intrazeolite photooxygenation of trisubstituted alkenes, the competing photooxygenation of l-phenyl-3-methyl-2-butene and its geminal methyl deuteriated analogues (Scheme 44) was studied . ... 

TABLE 21. Regiochemistry in the intrazeolite photooxygenation of electron-poor alkenes 133-136"... 

TABLE 19. Regioselectivity in the intrazeolite photooxygenation of deuterium labelled trisubstituted alkenes ... 

The regioselectivity in the ene reaction has been reviewed.1295 The intrazeolitic photooxygenation of alkenes to produce hydroperoxides has attracted considerable... 

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