Electron-transfer deoxygenation, photoinduced

PHOTOINDUCED ELECTRON-TRANSFER DEOXYGENATION OF BENZOATES AND m-(TRIFLUOROMETHYL)BENZOATES WITH 9-ETHYL-3.6-DIMETHYLCARBAZOLE... 

Z. Wang, D. R. Prudhomme, J. R. Buck, M. Park, and C. J. Rizzo, Stereocontrolled syntheses of deoxyribonucleosides via photoinduced electron-transfer deoxygenation of benzoyl-protected ribo- and arabinonucleosides, J. Org. Chem., 65 (2000) 5969-5985. 

Prudhomme, D. R., Wang, Z., Rizzo, C. J. An Improved Photosensitizer for the Photoinduced Electron-Transfer Deoxygenation of Benzoates and m-(Trifluoromethyl)benzoates. J. Org. Chem. 1997, 62, 8257-8260. 

A. Chiocconi, C. Marino, E. Otal, and R. M. de Lederkremer, Photoinduced electron transfer and chemical a-deoxygenation of D-galactono-1,4-lactone. Synthesis of 2-deoxy-D-/yxo-hexo-furanosides, Carbohydr. Res., 337 (2002) 2119-2126. 

Sun et al. further investigated the photoinduced electron transfer reactions of C6o and triethylamine, both in deoxygenated solution and air saturated solution [79], Three types of cycloadducts of fullerenes 33 and 92a-b were obtained, whereas the formation of the monoalkylated l,2-dihydro[60]fullerene 29 as described by Liou et al. [230] in the reaction of trimethylamine and /V,/V-dimcthy-laniline with C6o, was not observed (see Fig. 32). 

A series of chlorophyll-like donor (a chlorin) linked having C60 (chlorin-C60) or porphyrin-C60 dyads with the same short spacer have been synthesized as shown in Schemes 13.1 and 13.2 [39, 40]. The photoinduced electron-transfer dynamics have been reported [39, 40]. A deoxygenated PhCN solution containing ZnCh-C60 gives rise upon a 388-nm laser pulse to a transient absorption maximum at 460 nm due to the singlet excited state of ZnCh [39]. The decay rate constant was determined as 1.0 X 10u s-1, which agrees with the value determined from fluorescence lifetime measurements [39]. This indicates that electron transfer from 1ZnCh to C60 occurs rapidly to form the CS state, ZnCh +-C60 . The CS state has absorption maxima at 790 and 1000 nm due ZnCh+ and C60, ... 

The mechanism of the photoinduced decarboxylation of pyruvic acid has been reinvestigated and accounted for via electron transfer from an excited to a ground state molecule. Quantum yields of triplet production at 295 K in deoxygenated benzene, acetonitrile, and water are 0.65, 0.88, and 0.22, respectively. ... 

As a last example of fuUerene functionalization leading to pyrroUdinofuUerenes, the photoreaction of triethylamine (TEA) with should be discussed. FuUerene C50 undergoes efficient photochemical reactions with TEA to form a complex mixture of addition products under ambient and deoxygenated conditions.The reactions are initiated via photoinduced electron transfer between the excited singlet Qo and the amine. Three types of cycloadducts of fuUerenes — 50,51, and 52 — were obtained, whereas the formation of the mono-alkylated l,2-dihydro[60]fuUerene 53, as described by Liou etaL in the reaction of trimethylamine and N,N-dimethylanUine with C50, was not observed (see Figure 28.8). 

As discussed above (Section 66.3), phenacyl ester radical anions fragment readily to phenacyl radicals and carboxylate anions. The radical anions of benzoate esters also fragment to carboxylate anions and alkyl radicals, and this process is faster if the alkyl radical is stabilized (3°, benzyhc). This concept has been applied successfully to the deoxygenation of carbohydrate alcohols by photoinduced electron transfer (PET) sensitization. For instance, irradiation of 38 in water/2-propanol, using a substituted... 

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