SYNTHETIC CHEMISTRY WITH FULLERENES - PHOTOOXYGENATION OF OLEFINS

Under irradiation with visible or UV (>290 nm) light in the presence o f molecular oxygen and a minute amount of fullerenes, olefins and dien es undergo ene and Diels-Alder reactions with singlet oxygen to give p hotooxygenation products. The regio- and stereoselectivities of the ph otooxygenation of beta-myrcene, (+)-pulegone, 4-methylpent-3-en-2-ol, and (+)-limonene were very similar to those observed in known singlet oxygen reactions, indicating that the fullerene-sensitized reaction ge nerates free singlet oxygen. The efficiency of fullerenes and conventi onal sensitizers was qualitatively examined by using the Diels-Alder r eaction between O-1(2) and furan-2-carboxylic acid as a probe. Among t hose examined, C-70 was found to be the most effective. The reaction w as the fastest and completed with as little as 0.0001 equiv of C-70. C -60 and hematoporphyrin were found to be of similar efficiency. The me thanofullerene 13, which lacks one olefinic conjugation in the C-60 co re, was as good as C60 itself, but the aminofullerene 14, lacking six double bonds, was quite inferior. The fullerene carboxylic acid 15, wh ich was previously shown to show considerable biochemical activity, wa s found to be capable of generating singlet oxygen in aqueous DMSO.