Vinyl group, radical rearrangement

In radical rearrangements, the migrating groups are those that can accommodate electrons in a tt system (vinyl, aryl, carbonyl) or atoms that can expand their valence shell, i.e., all halogens but fluorine. Hydrogen and alkyl do not migrate to... 

Compared with their cationic counterparts, only a few radical rearrangements are fast enough to appear in synthesis. An example is vinyl migration in which a vinyl group migrates via the formation of the methylcyclopropyl intermediate (Scheme 2.12). 

Apart from cycHzation to cyclobutanols, type II 1,4-biradicals have been known to undergo radical cleavage from the a and 8 carbons, the latter being discussed more fully later. When a vinyl group is attached to the y-carbon, an aUyhc rearrangement occurs, producing a 1,6-biradical that can cychze to a cyclohexenol and disproportionate to a 5-acyl-2-hexene as well as form normal type II products (Scheme 10). 

Monomers of this type are expected to polymerize via their vinyl groups. However, their acetal groups may also participate in the free radical polymerization, since it is known that cyclic acetals such as shown below undergo a free radical ring opening rearrangement to the corresponding ester (24). 

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