Subject Radical-71-cyclization transform

Alkynes are interesting radical acceptors for cyclization reactions because the products contain double bonds that can be subjected to further transformations. In the case of terminal alkynes, the desired products can be obtained in high yields as single isomers. With non-terminal alkynes as acceptors, the alkene products are generated as mixtures of ( )- and (Z)-isomers in high yields but with low selectivity [36],... 

The Wittig-Horner olefination of the aldehyde 28 provided alkenes 29 which were subjected to radical cyclization leading to benzofused tricyclic j6-lactams 30, obtained as single diastereomers (Scheme 8) [36]. A convenient, direct regio- and stereoselective route to optically pure unusually fused or bridged tricyclic /3-lactams has been developed by the use of intramolecular nitrone-alkene cycloaddition reactions. For example, the aldehyde 21 can be transformed into nitrone 31 which subsequently was used for a variety... 

In addition to the aforementioned transformations, the photo-induced Bergman cyclization was utilized by Zhu and coworkers to form intramolecular polymeric nanoparticles.The appropriate reactive diyne unit was incorporated into the polymer using both direct controlled radical polymerization and aHqme protection strategies. The resulting linear polymers were subjected to photochemical Bergman cyclization conditions using a continuous addition strategy, similar to the case previously discussed. ... 

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