Alkene epoxidation radical-mediated

The above-mentioned important and impressive applications of titanocene mediated and catalyzed epoxide opening have been achieved by using the already classical 5-exo, 6-exo and 6-endo cyclizations with alkenes or alkynes as radical acceptors. Besides these achievements, the high chemoselectiv-ity of radical generation and slow reduction of the intermediate radicals by Cp2TiCl has resulted in some remarkable novel methodology. 

In 2002, however, it was observed that water did substantially affect radical cyclizations mediated by Ti(III) complexes. Thus, for example, when epoxide 20 was treated with Cp2TiCl in dry THF, the exocyclic alkene 21 was obtained. When the same epoxide was treated with CpaTiCl in the presence of water, however, the corresponding reduction product 22 was formed. Moreover, with deuterium oxide instead of water, the deuterium labeled isotopomer 23 (Scheme 18) was isolated [72],... 

The number of monomers that undergo chain-growth polymerization is large and includes such compounds as alkenes, alkynes, allenes, isocyanates, and cyclic compounds such as lactones, lactams, ethers, and epoxides. We concentrate on the chain-growth polymerizations of ethylene and substituted ethylenes and show how these compounds can be polymerized by radical and organometallic-mediated mechanisms. 

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