Photo-initiated radical allylation

Free-radical cyclopolymerization of diallyl or mixed allyl-vinyl and allyl-acrylic derivatives has been investigated. Particularly, Jansen has studied the photo-initiated copolymerization of various commercial vinylethers as well as allylethers with fumarates or maleates. Real-time infrared spectroscopy with advanced multivariate statistical techniques was used for the determination of copolymerization reactivity ratios of... 

Photo-polymerization was conducted at 254 nm under a modified fluorescent microscope. Allyl-oligonucleotides were employed with methylene blue as the free radical initiator for crosslinking. In the case of proteins, acryloyl streptavidin was first immobilized so that biotinylated proteins could be applied to the gel pad (Vasiliskov et al., 1999). One of the major drawbacks with the gel pad approach was that separate pads had to be manufactured instead of coating the enhre slide with the gel and then printing down the microarray. 

Olefins containing at least one allylic hydrogen are suitable substrates and are of special importance and interest with regard to the intrinsic mechanism involved in their reactions with singlet oxygen. Allylic hydroperoxides are formed, but the mechanism of their formation is clearly distinct from that by which allylic hydroperoxides are produced in thermal or photochemically initiated (see example above for a Type I process) autoxidation reactions. This has unequivocally been shown with optically active limonene as a substrate, which gives rise to different products in free radical and Type II photo-oxygenation reactions (22, 57, 61). 

Oxidation of methyl oleate has been extensively studied and is considered to be typical of all monoene acids/esters. Photo-oxygenation produces only two products - the 9-hydroperoxide (AlOt) and the 10-hydroperoxide (A8t) - in equal amounts. Reaction is confined to the olefinic carbon atoms and is accompanied by double-bond migration and stereomutation. As shown in Scheme 10.5 autoxidation of methyl oleate forms eight monohydroperoxides of which two (9-OOH A 10c and lO-OOH A8c) are only minor products. This range of compounds arises from initial attack at either allylic carbon atom to give a delocalized radical with oxygen finally attached to any one of four carbon atoms. 

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