Sensitizers rose Bengal

Lee, P.C.C. and Rodgers, M.A.J. (1987). Laser flash photoki-netic studies of rose bengal sensitized photodynamic interactions of nucleotides and DNA. Photochem. Photobiol. 45, 79-86. 

Baeckstrom and coworkers utilized the enhanced selectivity of singlet oxygen towards different types of double bonds, as the key step for the synthesis of trani-Sabinene . By using the method of simultaneous oxidation and reduction (Rose Bengal sensitized photooxidation in the presence of tetrabutylammonium borohydride) they managed to isolate compound 166 by a total conversion of 164 (Scheme 61). Compound 165 remained... 

Risk labels, lATA/ICAO, 751-3 Risk phrases, 621, 748, 749 River water, peroxide determination, 642 RNA, ozone disinfection, 616 ROS see Reactive oxygen species Rose Bengal sensitized photooxidation, 890 Rotational barriers, regioselective allylic hydroperoxide formation, 836, 847-9 Rotational isomers, peroxynitrous add, 8-9 Rotational spectra, ozonides, 721, 722-3 RP-HPLC, hydrogen peroxide determination, 627... 

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) ... 

In sensitized or photocatalyzed reactions, conditions of total or constant absorbance can easily be controlled by the concentration of the sensitizer or photocatalyst added. In addition, experience has shown that the concept of spatial separation between the light source and the reaction mixture is in general not required. Dragoco uses immersion-type annular reactor geometries [2, 3, 69, 70] for the production of ( —)-rose oxide by rose bengal sensitized oxidation of (— )-citronellol (Eqs. 45-48, Figure 23). 

Rose-Bengal sensitized photooxygenation of cyclic tryptophan derivative 119 gave l,3-diazocine-2,6-dione 120 (76H53). Murato and coworkers reductively cleaved / -carboline derivative 121 and isolated the novel diazocinoindole 122 (77CPB1559). 

Figure 2. Quantum yields of the Rose Bengal sensitized photooxidation of Q shown in a plot derived from Equation 39.

The reactions of (31) and (39) with molecular oxygen has been investigated in some detail 208,2U). The reaction products for the autoxidation and rose bengale sensitized oxidation are shown below. 

The synthetic potential of singlet oxygen may be used to effect the conversion of dimethyl 1-(nitromethyl)alkyIphosphonates into dimethyl 1-formylalkylphosphonates. Thus, treatment of a Rose Bengal-sensitized solution of dimethyl l-(nitromethyl)ethylphosphonate and MeONa in MeOH with singlet oxygen affords dimethyl 1-formylethyIphosphonate in 80% yield. A temperature dependence of the yield has been observed. For the reaction with dimethyl l-(nitromethyl)eth-ylphosphonate in MeOH at 10°C, 0°C, and -78°C, the conversions are 50%, 60%, and 100%, respectively. The higher yield at low temperature may reflect increased stability of the intermediate... 

Such a process can produce 02( Ag) with 80% efficiency and similar reactions involving peroxide decomposition have been documented [21]. Of particular interest is the use of the decomposition of the endoperoxides of aromatic compounds, which, when appropriately substituted can be used in water [22] and of water soluble phosphite/ozone adducts [23]. Such chemical methods can provide a critical control for reactions in which photoexcitation of a sensitizer is suspected of doing more than just produce 02(1Ag). A prime example involves the rose bengal sensitized photooxidation of relatively unreactive alkenes [24],... 

It has been found that certain dyes, such as methylene blue, eosin and Rose Bengal, sensitize the photo-oxidation of many organic compounds in solution [Refs. 242, 246-248, 328, 329, 371, 585, 639, 668]. More detailed investigations have shown that the photo-oxidation reaction takes place with the participation of singlet oxygen formed by the reaction between the dye excited to the triplet state and molecular oxygen. The energy of the triplet state dye molecules (Table 15) is sufficient to... 

The rose bengal-sensitized photooxygenation of 2-methoxynorbornene (196) in acetaldehyde at — 78°C is the archetype (Scheme 26) <83JA6498, 84MI 620-02>. The aldehydic ester, (197) (31% yield), and the pair of cw-fused epimeric trioxanes (198) (13% yield) are obtained. The result is interpreted... 

The enol ether (230) has features in common with (223) in that they both encompass part of the artemisinin skeleton. Rose bengal-sensitized photooxygenation of (230) in THF containing acetaldehyde is reported to give the pair of (35) 3-methyl trioxanes (231) (35% yield) which are epimeric at C5 (Equation (34)) <88CC372>. Paradoxically, when photooxygenation is carried out in methanol followed by acid hydrolysis, the secoartemisinin derivative (232) (15% yield) is formed in which the C(3) methyl substituent has the 3R configuration (Equation (35)). The structures of the 35,55 epimer of (231), and (232) are established by x-ray. 

The rose-bengal-sensitized photo-oxygenation of aziridines (240) in MeOH gave phthalimide (242) (51%) as the only isolable product.The mechanism... 

Recently, scale-up of photochemical reactions has significantly advanced, thanks to the development of microreactor technology. In the field of singlet oxygen, the first example in 2002 was the rose bengal-sensitized photooxidation of a-terpinene in a glass microchip [54]. Eighty percent conversion was obtained... 

Valence tautomerization of pyrimidine-alkyne photoadducts is mediated by treatment with trimethylsilyl chloride/hexamethyldisilazane, followed by silica gel, affording diazocin-2,4-dione derivatives (8) in good yield (vide supra) <82TL4207,83JOC2337). Oxidative cleavage of a bicyclic diaza compound by rose Bengal-sensitized addition of oxygen affords the benzo-3,4-dihydro-1,3-diazocin-2,6(17/,5//)-dione derivative (38) (Equation (15)) <87H(26)2477>. 

Oxidation of selenides. lenides are converted into selenoxides in high yield by oxidation with singlet oxygen (Rose Bengal sensitizer, CH3OH). In the case of -hydroxy selenides, elimination of RSeOH occurs to some extent to form allylic alcohols. ... 

Photolysis of a benzene solution of chloranil and N gave rise to the norbornene analogues of 7,8, and 10 and the tricyclene derivative 9. By contrast, in acetonitrile solution, formation of only small amounts of type 8 and 9 adducts was detected/ The photoreaction of chloranil and Q gave rise to the type 7 adduct as the sole product. Irradiation of Q in acetone or methanol solution under Rose Bengal-sensitized (RB) conditions generated about 70% of N and adducts 11 and 12. ... 

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