Rose Bengal decarboxylation

The reader may, perhaps, recognize 8 as being a derivative prepared from Rose Bengal which is first decarboxylated and then acetylated. We refer to 8 as RBAX. RBAX is a xanthone, analogous to the thioxanthones which are common commercial UV photoinitiators. The latter are used with typical... 

Figure 6. Rate of heat evolution during argon-ion laser-photoinitiated polymerization of 1-methyl-2-pyrrolidinone (MP), 9 ML of 2-ethyl-2-(hydroxymethyl)-l,3-propanediol triacrylate (TMPTA), and the dyes at a concentration of 10 m. Initiators 1) 19, 2) 18, 3) 10, 4) 16, 5) RBAX (rose bengal derivative prepared from rose bengal, which is first decarboxylated and then acetylated [36]),...

The first such system employed a neutral electron acceptor RBAX (Figure 17) (a derivative of rose bengal, prepared first by decarboxylation, and then acetylation)... 

The Z-alkene in the other half 257 was made from a furan 262. Cycloaddition with singlet oxygen (rose Bengal is a dye that sensitises the conversion of normal triplet oxygen to the singlet) leaves one necessarily Z-alkene in the five-membered ring 264. One possible mechanism for the decarboxylation of the cycloadduct 263 is given 265. 

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