Rose bengal, oxygen sensitizer

The intermolecular and intramolecular 13C isotope effects were used in studies of the mechanism of the ene reaction of singlet (1Ag) oxygen with alkenes.89 The intermolecular 13C isotope effect was determined for reaction of 3-isopropyl-2,4-dimethylpent-2-ene 40 with 102 in methanol/2-propanol (1 1) at 10°C using a sunlamp and Rose Bengal as sensitizer. 

Compound (362) gave the trioxane (19) (15%) when reacted with singlet oxygen in the presence of acetaldehyde, using rose bengal as sensitizer, followed by treatment with HC1 (88CC372). 

A 2% solution of isoprene in dichloromethane and methanol with methylene blue or rose bengal as sensitizers gives, on irradiation under oxygen with a 500-W iodine lamp, a 50% yield of 4-methyl-l,2-dioxa-4-cyclohexene [52]. Cyclic dienes are converted into bicyclic endoperoxides (equation 132). The naturally occurring ascaridole is thus synthesized from a-terpinene (equation 133) [19, 1115]. 

Photo-oxidation of the imino-ether (118) (prepared from yohimbine via the 7-chloroindolenine derivative), in the presence of oxygen and potassium cyanide, with Rose Bengal as sensitizer, results in the introduction of a cyano-group into the tryptophan position the product is thus the a-amino-nitrile (119), together... 

The oxidation products mentioned can also be obtained by oxidation of hexahydrocolupulone with singlet oxygen, which is generated by Irradiation with visible light using Rose Bengal as sensitizer (160). The conversion of the substrate is almost quantitative, but the amounts of hydroperoxide 207 and 4-hydroxy-... 

The role of rose bengal and other sensitizer dyes in the photodimerization of 2-acet5i-l,4-benzoquinone [1125-55-9] involves electron transfer but not singlet oxygen (42) (see Dyes, SENSITIZING). 

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... 

Competitive photooxygenation of the substrate pair 1-methyl-cyclopentene (AJ/l-methylcyclohexene (A2) was studied by Kopecky and Reich.123 Using rose bengal, erythrosin, and eosin, as well as methylene blue and hematoporphyrin as sensitizers, the ratio kg1/kg2 was found to be independent of the nature of the sensitizer used, in agreement with the assumption that singlet oxygen is the oxygenating intermediate. 

As indicated above, considerable efforts in research and development have been deployed into the development of insoluble singlet oxygen sensitizers. Although, rose bengal chemically bound to chloromethylated copolymer of styrene and di vinyl benzene [14, 84] (and commercialized as Sensitox ) has shown excellent results as far as its light stability in solid matrices is concerned [85], the sensitizer is suffering, in addition to the drawbacks of the... 

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