Approaches to Stereoselective Dioxygenation of Alkenes: Chiral Phosphite Ozonides
作者:Patrick H. Dussault、Kevin R. Woller
DOI:10.1021/jo961564h
日期:1997.3.1
Synthetic Chemistry with Fullerenes. Photooxygenation of Olefins
作者:Hidetoshi Tokuyama、Eiichi Nakamura
DOI:10.1021/jo00084a036
日期:1994.3
Under irradiation with visible or UV (>290 nm) light in the presence of molecular oxygen and a minute amount of fullerenes, olefins and dienes undergo ene and Diels-Alder reactions with singlet oxygen to give photooxygenation products. The regio- and stereoselectivities of the photooxygenation 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 generates free singlet oxygen. The efficiency of fullerenes and conventional sensitizers was qualitatively examined by using the Diels-Alder reaction between O-1(2) and furan-2-carboxylic acid as a probe. Among those examined, C-70 was found to be the most effective. The reaction was 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 methanofullerene 13, which lacks one olefinic conjugation in the C-60 core, was as good as C60 itself, but the aminofullerene 14, lacking six double bonds, was quite inferior. The fullerene carboxylic acid 15, which was previously shown to show considerable biochemical activity, was found to be capable of generating singlet oxygen in aqueous DMSO.
Sensitized photo-oxygenation of a wide variety of acyclic 1,3-dienes was investigated. The 1,4-cycloaddition of singlet oxygen to acyclic conjugated dienes was closely related to the thermal Diels-Alder reaction in stereospecificity, and steric and electronic effects of substituents. Reactivity order of singlet oxygen toward conjugated dienes and isolated C—C double bonds was exhibited as follows:
A C60 derivative bearing an organofluorine tail through the dimethylsilyl moiety (1) was proved to be an efficient photosensitizer in C6F6. Photooxygenation of olefins or dienes was accomplished by catalysis of 1 (0.5–1.5 mol%) at room temperature under an oxygen atmosphere.